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Landscape, Floriculture, and Ornamentals News

Date Last Edited:  08/24/2001

Hawaii Cooperative Extension Service

No. 8, July, 2000


Kenneth W. Leonhardt, leonhard@hawaii.edu
CTAHR Extension Specialist in Horticulture

James C. Deputy, deputy@hawaii.edu
CTAHR Education Specialist

Kent Kobayashi, kentko@hawaii.edu
Dept. of Tropical Plant and Soil Sciences, CTAHR, Univ. of Hawaii


Jay Deputy, deputy@hawaii.edu
Education Specialist, CTAHR

The state's first certification test in the Certified Landscape Technician Program was conducted at Kona's Kealakehe High School on Saturday, April 29, 2000. Local contractor and program director Garrett Webb orchestrated a very busy day-long series of written and hands-on tests covering all aspects of landscape maintenance and installation. Thirty-nine professionals from the green industry, agricultural supply industry, and the University of Hawaii volunteered their time to serve as judges and other officials. Much of the equipment was loaned or donated by the local industry.

A total of 41 applicants paid $150 each to take the State's first offering of certification as a Landscape Technician in landscape maintenance. Thirty-six applicants had attended classes that were offered in Kona and in Hilo over the past eight months to prepare them for the test. Five other brave soles came to take their chances based on years of experience and without the benefit of the classes. However, upon registration, all applicants were provided with a "Test Book" which provided information on the content of the test, testing procedures, and tasks that the applicants would be asked to perform. A training manual, based on the material presented in the classes, was also made available to all who took the test.

During the 12-hour day, each applicant completed a two-hour written exam, and seventeen hands-on "problems". The problems required them to follow accepted safety procedures to properly operate various pieces of equipment, repair a broken irrigation line, set an assigned direction for a number of different types of sprinkler heads, and adjust the automatic scheduling for an irrigation system. They were also required to calculate and properly administer the correct amount of pesticide and fertilizer over a give area, follow proper techniques in pruning trees and scrubs, plant and stake a tree, install turfgrass sod, back and maneuver a truck and trailer, and identify 30 landscape plants.

An applicant must pass all parts of the exam in order to become a Certified Landscape Technician in maintenance. In similar certification tests on the mainland, the average number of applicants receiving certification is typically lower than 20%. In Hawaii's first offering, 3 out of the 36 applicants actually taking the test have passed all portions of the exam and received their certification. Many of the applicants passed all but two or three portions.

Any applicant who did not receive certification as a result of the first test may become certified by retaking and passing only the parts of the exam they failed. The cost for retaking one problem is $25; 2 problems is $30, 3 problems is $35, 4 problems is $40, 5 problems is $45, and 6 or more problems is $50. The next CLT test is tentatively scheduled for around September on the Big Island, March on Maui, and May on Oahu.

CLT programs expand to Oahu and Maui

The CLT program leading to certification in landscape maintenance has received additional funding from the State of Hawaii Employment and Training Fund to expand that part of the program to Oahu and Maui. The projects on both islands will be funded as pilot projects for one year with the intention of developing a self-sustaining program in future years, similar to the pilot project recently completed on the Big Island.

The Program Director of the state CLT program will continue to be Garrett Webb, and Diana Duff will serve as State Training Coordinator. In addition, a pilot program leading to certification in landscape irrigation will be offered in Kona beginning this summer. Funding for this project is also coming from the State of Hawaii Employment and Training Fund. Schedules for classes in both programs will be announced soon. The next certification test for maintenance and the first test in irrigation to be given in Kona will also be announced at a later date.

The Oahu and Maui pilot projects in maintenance are currently being organized. An advisory committee has been appointed for each island under the direction of Hawaii Landscape and Irrigation Contractors Association (HLICA) on Oahu, and Maui Association of Landscape Professionals (MALP) on Maui. One of the first duties of each committee will be to hire a Program Coordinator for their island.

Programs on both islands will follow the same general format of the Big Island program just completed. A series of 12 individual three-hour classes will be offered in different subject matter areas. Maui will offer two series of classes beginning around September of this year and concluding in February of 2001. A certification test in maintenance will then be given somewhere on Maui in March of 2001.

The Oahu program will offer a total of six series of 12 three-hour classes beginning in September of this year and concluding in late March or April 2001. A certification test in maintenance will then be given somewhere on Oahu in late April or May of 2001.

The ultimate goal is to develop certification programs in landscape maintenance, irrigation, and possibly landscape construction on all three islands. Pilot projects in irrigation will begin on Oahu and Maui when the program becomes self-sustaining in late 2001. A certification in landscape construction may be added to the program in the future. Continuation of all programs past the first year of funding is completely dependent upon the income generated by the program, and hopefully from additional industry support. Ideally, the administration of the entire program will eventually come under the general supervision of LICH and be driven by the industry. If successful, this program could become the major training ground for a significant portion of Hawaii's green industry.

Anyone interested in taking the courses, or grounds maintenance supervisors who want to send employees to the courses should contact Jay Deputy, deputy@hawaii.edu, at (808) 956-2150. The program also needs volunteer instructors, judges, and loan of equipment.

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A USDA-CSREES Special Grant Progress Report A USDA-CSREES Special Grant Progress Report

Ken Leonhardt, leonhard@hawaii.edu
Tropical Plant and Soil Sciences, CTAHR

The Hawaii tropical flower and foliage industry has been federally supported by the Hawaii Floriculture Research Grant since 1996. This grant includes anthurium, orchids, flowering ginger, bird of paradise, heliconia, protea, and foliage (ti leaves and other greens), both cut and potted, and is currently funded for $250,000. The Hawaii tropical flower and foliage industry is valued at more than $57 million in grower sales with out-of-state sales as the primary market. Since the early 1970s, the floral and nursery crops industry in Hawaii, particularly cut flowers, orchids, and foliage, has been recognized as a major increasing portion of Hawaii's agriculture.

The program objectives of this grant, and its individual sub-projects were developed in a series of meetings of CTAHR faculty and industry representatives. An industry Federal Floriculture Advisory Committee was established to select proposals that best address the program thrust and objectives and annually evaluate progress. The objectives of the entire project are to:

  • Develop and commercialize high yielding disease and pest resistant floral cultivars with unique horticultural qualities that can keep the Hawaii cut-flower industry ahead of the competition.

  • Address current technical constraints such as quarantine issues that limit the export of Hawaii floral crops.

  • Develop strategic marketing responses that include identification of market opportunities and strategies for market penetration, based on an analysis of the strengths and weaknesses of Hawaii's competitive position.

Brief Progress Reports Brief Progress Reports

Ken Leonhardt, CTAHR, and Principal Investigator for the protea cultivar development project, reported that in 1999 the following seven new pin cushion protea (Leucospermum) hybrids were released to growers in Hawaii:

UH Hybrid no.--Parents--Brief description

UH 72--L. Spider x L. T88-09-02--Orange pins, red ribbons. Blooms 9 months.

UH 82--L. Rachel x L. saxosum--Flower color and shape similar to UH 24. Long narrow stems. Maroon new foliage. Blooms Dec.-Mar. Appears elsinoe resistant, but not tested yet.

UH 89--L. UH 58 x L. Tango--Deep red with white "frost" on ribbons. Shape like UH 24. Blooms almost year round.

UH 104--L. Ballerina x L. UH 31--Dark orange pins, metallic ribbons. Slender stems and leaves. Shape like Scarlet Ribbon. Heavy bloomer, Jan.-June.

UH 105--L. Ballerina x L. UH 31--Orange pins, blood red ribbons. Heavy bloomer, Jan.-June. Sibling of UH 104.

UH 133--L. T88-09-02 x L. UH 49--Dark yellow pins, dark orange ribbons. Blooms Dec.-June.

UH 135--L. T88-09-02 x L. Spider--Yellow pins and ribbons. Flower shape like Spider. Heavy bloomer, Nov.-June.

Heidi Kuehnle, heidi@hawaii.edu, CTAHR, Principal Investigator for the anthurium and dendrobium breeding programs, reported the release of a new anthurium, 'Mauna Loa' (UH1155), a disease-resistant, easy-to-micropropagate, glossy white obake cut flower with an excellent vaselife of 40 days after packing.

The dendrobium breeding program released the following two new varieties:

D. Winifred Ogata (UH1371), is a two-tone lavender, seed-propagated potted cultivar with peak flowering during fall and early winter. Flowers that measure 31/2 inches across lasted exceptionally long on plants at 85 days.

D. Ethel Kamemoto 'White Cascade', is a floriferous, short statured potted plant, bearing paper-white pansy lip flowers with fall and winter flowering. Flowers remain attractive for two months or longer.

Over 300 seed pods of 18 different cutflower and potted plant cultivars were provided to three dendrobium grower associations in 1999. In addition, four flasks of D. Ethel Kamemoto 'Splendor' and 21 flasks of D. Ethel Kamemoto 'White Cascade' protocorm-like bodies were provided. All of the anthurium and dendrobium introductions from CTAHR, current and past, were developed and selected by Professor Emeritus Haruyuki Kamemoto.

Hawaii is home to many alien insect pests that are of quarantine significance worldwide. Despite the use of toxic insecticides, quarantine rejections cost the floriculture industry more than $3.0 million from 1990-1994 and limited our markets. The following projects of Arnold Hara and Robert Paull have led to the development of postharvest handling systems that reduce reliance on toxic chemicals while increasing quarantine security and product quality.

Arnold Hara, arnold@hawaii.edu, CTAHR, is the Principal Investigator of the project, Postharvest Handling Systems for Pest Disinfestation of Hawaiian Floriculture Crops. His Co-Investigators are Robert Paull, paull@hawaii.edu, and Brent Sipes, sipes@hawaii.edu, CTAHR, and Marcel Tsang, marcel@hawaii.edu, UH-Hilo. Hara reports the following results:

Hot air and hot water treatments

Efficacy tests were conducted to determine temperature and time requirements for disinfesting commodities of various insects in hot air. For example, western flower thrips (WFT), Frankliniella occidentalis, adults were not able to survive longer than 90 min when subjected to 44°C hot air. These results show promise because chrysanthemums, commonly infested with WFT, can withstand this treatment with no loss of marketability or vase life. Work continues to verify that egg, larvae and pupae of WFT are controlled with this treatment.

Dracaena, philodendron, veined croton, spotted croton and podocarpus foliages subjected to either hot-water treatment alone (49°C, l2 min) or hot-air conditioning (44°C, 2 h) plus hot-water treatment showed no significant differences in marketability or vase life as compared with foliages receiving no treatment. Hot water temperature profiles of hot water drenches demonstrated that 6-inch potted anthuriums (50% peat/50% perlite) will reach the target temperature of 50°C in less than two min. Cooling for 10 min in ambient water drenches immediately after hot water drenching, was enough to return the potting media to ambient temperature. No water cooling allowed the potting media to remain above 45°C at 10 min after hot water drenching. Efficacy of the hot water drench at 49°C (15 min) and 50°C (10, 15, 20 min) against the burrowing nematode in roots and stems of potted anthurium (Ozaki, Tropic Lime, Ellison Orizuka) showed 95 to 100% reduction after hot water drench. The hot water drench had minimal negative effects on the growth (measured by number of new leaves, root and stem weight) of potted anthuriums (Marian Seefiirth, Pink Aristocrat, UH 927, Pele), but not significant to affect the overall market quality. This treatment can be successfully used on these cut foliages.

Both monstera and whaleback foliages benefited from conditioning prior to hot-water immersion and showed a trend of extended vase life beyond hot-water treatment alone. Pothos foliage, on the other hand, tended to have longer vase life with no conditioning prior to hot-water immersion. Among all three foliages, those receiving no treatment tended to have the longest vase life. Hot-air treatment alone might be a more appropriate treatment for these three foliages due to their slight sensitivity to hot water.

Three grower/shippers who have implemented hot water treatment for 1 to 2 years (1997-1999) have reduced dollar loss due to quarantine rejected shipments by 50%, decreased labor requirements and lowered postharvest insecticidal dip by 80 to 90%. These grower/shippers represent 14% of the floriculture industry and 8% of the export floriculture industry. Three additional grower/shippers who represent a major portion of shipments from Hawaii to California will have implemented hot water treatment in 2000.

Testing of Dursban® for thrips control

Efficacy tests were concluded with Dursban granules performing similarly to previous trials; after 75 days post treatment, Dursban 20 was still significantly reducing the degree of thrips injury in anthurium flowers. Only a treatment that combined Mavrik® as a foliar spray and Dursban 20 was more effective. Dursban is currently under EPA, FQPA review and could possibly have its use reduced in the future. Registration for use on anthuriums and other ornamentals is currently on hold pending the EPA findings.

In-field pest management studies

Soil applied fipronil and chiorpyrifos formulations were evaluated against 8 species of ants in red ginger flowers. The first evaluation conducted 7 days after treatment found plots treated with fipronil G (EXP6 1 748A) applied either at 0.01875 or 0.025 lb Al/acre and chlorpyrifos (Dursban 50 WSP) sprayed at 0.5 lb Al/acre had significantly less flowers infested with ants as compared with untreated plots. When the trial was concluded 35 days after treatment and after more than 37 inches of rain had fallen, Dursban 2CG, fipronil G, and fipronil 8OWG still had a significantly reduced incidence of flowers with ants.

Conserve® SC, Cinnamite®, Floramite®, and Avid® 0.15 EC were evaluated against the citrus red mite, Panonychus citri, infesting anthuriums. Conserve was not effective against the citrus red mite, while Cinnamite, Floramite, and Avid treatments reduced the numbers of mites per leaf 7 days after treatment. Throughout the trial Floramite and Avid provided the most control and still remained effective 28 days after treatment.

Potting containers coated with latex paint containing Talstar® (bifenthrin) and Spinout® (copper hydroxide) were evaluated for their ability to control root mealybug, Rhizoecus hibisci, in potted palms. Talstar is a synthetic pyrethroid labeled for use on ornamentals. Spinout chemically prunes roots that contact the inner coated pot surface. This root pruning process keeps plants from becoming pot bound by eliminating the problem of swirling roots between the media and the container's interior. Both curative and preventative trials were conducted. In the curative trial, the degree of root mealybug infestation was reduced over time in plants grown in treated containers. Also, there was a lower incidence of new infestations developing in plants growing in the coated containers. Although the treatments were not completely effective, they showed promise and could possibly be integrated with other control strategies for this difficult to control pest.

Insecticide phytotoxicity tests

Cinnamite®, a new product derived from synthetic cinnamon oil, was tested for its safety to anthurium and orchid plants. 'Uniwai Pearl', 'Uniwai Supreme', and 'Uniwai Princess' dendrobium cultivars and two cymbidium cultivars (yellow and wine colored) all proved to tolerate Cinnamite at 2X the recommended rate. Tests on 'Ellison Onizuka' and 'Rainbow Obake' anthuriums was also negative for phytotoxicity. Screening of additional anthurium cultivars is planned for this year.

A supplemental label was recently added to Dimethoate® 400, one of the few available systemic organophosphate insecticide, to include its use on general ornamentals. Phytotoxicity tests were conducted to verify its safety to certain Hawaii ornamentals. Dendrobium 'Uniwai Pearl', 'Uniwai Supreme', and 'Uniwai Princess' cultivars all tolerated four weekly foliar applications at twice the labeled rate. 'Song of India', 'Janet Craig', 'Massangeana', and 'Warneckii' dracaena cultivars and sago, areca, Macarthur, phoenix, fishtail, and coconut palms all showed no phytotoxic reactions to dimethoate. However, chrysanthemums developed chlorotic leaves and some stunting after foliar applications and should not be treated with this product. This chemical was previously available to anthurium growers through an SLN label for control of thrips and has proved to be safe on anthuriums.

Notice of Treatment Stamp for Hot Water Dip Approved by California Department of Food and Agriculture

A pest exclusion advisory was issued by the California Dept. of Food and Agriculture (CDFA) in September 1999, notifying all County Agricultural Commissioners the NOT (Notice of Treatment) stamp for products dipped in hot water was approved. CDFA states, "Shipments of certain Hawaiian cut flowers and greens may be successfully treated with hot water in order to kill surface pests. This treatment physically kills the target pests even though they may appear fresh. Movement, except for scales, is an indication that the treatment failed and the insect is alive. For scales it must be determined the pharyngeal (food) pump is functioning (to confirm live scale insects) by a qualified entomologist. Specimens must be submitted with the host material and without being exposed to a killing agent (e.g., alcohol)."

The approval of the hot water dip is the culmination of five years of research that began with test shipments to CDFA. In test shipments of hot water treated cut flowers and foliage, Dr. Ray Gill, CDFA Entomologist, was convinced of the effectiveness. After 3 test shipments, Dr. Gill concluded, "This hot water treatment of cut flowers and florals certainly appears to have merit in controlling an otherwise serious problem with those insect pests that could hitchhike on these plants."

A Hawaiian flower shipper who uses the hot water dip commented, "Shipments with the NOT stamp are not being held for agricultural inspections expediting deliveries to customers."

Robert Paull, paull@hawaii.edu, CTAHR, is the Principal Investigator of the project, Postharvest Handling Systems for Improved Quality of Hawaiian Floricultural Crops. He reported that the major event in his lab this year was his graduate student Theeranuch "Kai" Chantrachit completing her PhD in horticulture, submitted to the Graduate Division of the University of Hawaii in August 1999. The following is an abstract of her dissertation, "Post-harvest Physiology of Red Ginger Inflorescence (Alpinia Purpurata Vieill K. Schum)":

"The postharvest physiology of red ginger inflorescence, including the impact of heat treatment to extend inflorescence vase life, was determined. More than 90% of the inflorescences showed inflorescence wilting or bract browning symptoms, or both, during senescence. Ethylene and the total count of microorganisms in the stem segments as well as the vase solution had no effect on the development of senescence symptoms. I hypothesized that water balance of the cut stem was associated with inflorescence wilting, whereas sugar content was associated with bract browning symptom. While a relationship between inflorescence wilting and water balance was not confirmed, a positive relationship was established between sugar content and inflorescence vase life, as the higher the sugar content in cut stem, the longer the inflorescence vase life."

"Immersion of the inflorescences in hot water at 40°C for 15 min is recommended as a preconditioning treatment to prevent heat damage to red ginger from the hot water treatment at 50°C for 12 min for insect disinfestation. This combination treatment extends vase life. Extension of inflorescence vase life by the hot water treatment varied with season of harvest and flower variety. Exposure time shorter than 12 min at 50°C was recommended in winter, as the inflorescences had lower thermotolerance than in the summer."

"Hot water treated inflorescences exhibited a lower rate of respiration than untreated inflorescence, while ethylene production as a result of the treatment was not significantly detected. Inflorescences treated with hot water maintained higher sugar levels for a longer period than untreated inflorescences, and this could explain the vase life extension. Hot water treatment also suppressed negative geotropism in the red ginger inflorescences during horizontal storage. The negative geotropic response was delayed for up to 7 days after the hot water treatment."

"It was found that 98% of the sugar content in the red ginger stem was located in the symplast. The remaining two percent was attributed to the apoplast, which seems to be heat resistant since the contents of this region were not affected by the hot water treatment. Sugar metabolism in red ginger inflorescence may be heat sensitive. However, the activity of sugar metabolic enzymes sucrose phosphate synthase, sucrose synthase and invertase, were not directly related to the changes in sugar content after hot water treatment. It is therefore suggested that factors other than the activity of these enzymes affect sugar content of the cut stem."

A second phase of Dr. Paull's postharvest project addresses the suppression of bacterial and other microbial infections that attack the cut flower.

Bacteria, yeasts and other microbes are found everywhere, in soil, decaying vegetation and water. Bacteria can rapidly grow in the water of containers containing flowers. It is known that when the number of microbes increase beyond a certain point, flower postharvest life is reduced due to restriction of water movement in the stem. The food for this microbial growth is provided from the broken cells at the cut surface. Removal of a 1" section of stem from the base of a cut flower removes most of the contaminating bacteria. Placing this stem back into water starts the process of contamination all over again.

It is therefore crucial to minimize bacterial growth. Most commercial preservatives contain an antimicrobial compound. Household bleach (sodium hypochlorite) is an excellent disinfecting solution. These solutions are normally 5% to 5.25% active ingredient. The addition of bleach to the flower holding solutions has been recommended for many cut flowers. The concentration used in the holding solution is between 50 and 100 ppm (1 to 2 teaspoons per 8 gallons). However, these concentrations cause a significant reduction in anthurium flower vase life. Anthurium leaf and dendrobium sprays may also show a slight reduction. There is no effect of these concentrations on the vase life of heliconia, pincushion protea, red ginger and bird-of-paradise, and can be used safely with these flowers. Bleach can be used for anthurium, anthurium leaf and dendrobium spray, if the following procedure is followed. The buckets should be filled the night before they are to be used. The bleach (1 teaspoon per 8 gallons) is added at this time, by the next morning the chlorine concentration will be at safe levels when the buckets are to be used to hold flowers.

Bird of Paradise often shows saprophytic fungal growth on the boat and florets during shipping. The fungi grow on a slime produced during the floret's exit from the boat and also on nectar produced during floret opening. We determined that the amount of both the nectar and slime produced does not significantly vary throughout the year, however, the stage of flower development does significantly effect the amount produced. Older flowers produce 2 to 5 fold more nectar and slime than younger flowers. While production of nectar and slime was lower in younger flowers, the percentage of pale almost white florets was higher (66%) compared to florets from mature and older stages. The vase life of older flowers was also slightly greater than flowers at younger stages. This suggested that the maturity of the flowers had a significant effect on the production of nectar and slime, which affects the vase life of the Bird of Paradise. The greater the maturity, the greater the nectar and slime production becomes and the longer the vase life. It may be possible to minimize the nectar production but the slime is involved in lubricating the floret as it exits the enclosing boat bract. Although the fungal infection of the boat and florets does not seem to shorten the shelf life, it is very unsightly. This has led to the recommendation for a postharvest fungicidal treatment, where Bird of Paradise are trimmed to a stem length of 60 to 120 cm before the application of benomyl or thiabendazole fungicide.

Bird of Paradise vase life ranges from 10 to 14 days, this limits the marketing opportunities for this flower. Several trials were conducted to test short-term exposure (pulsing) to different solutions and the longer term holding solutions. Pulsing solutions overnight did not greatly affect postharvest life. Sucrose (5% w/w) in longer term holding solutions was very important for extending the vase life of the Bird of Paradise. Other solutions need to be studied in an overnight-pulsing treatment. Stem length had a slight effect on vase life, the longer the stem, the longer the vase life. Hot water treatment (preconditioning at 40°C, 15 mm, then 50°C, 12 mm) does not extend flower vase life.

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Jay Deputy, deputy@hawaii.edu
Education Specialist, CTAHR

Two of the most common problems that turf managers in Hawaii face are soil compaction and heavy thatch buildup in turfgrass. Thatch buildup is most commonly caused by over watering and heavy nitrogen fertilization on highly manicured turf. Although the production of some thatch is normal and actually beneficial, anything more than one half inch thick can lead to insect infestation, fungal diseases, and a greater susceptibility to scalping.

Soil compaction can also be a turf manager's nightmare. Traffic, weather condition and normal use push soil particles closer together, reducing pore space and increasing soil density. Due to decreased air, water and nutrient movement, turf roots struggle to fill their basic needs. As a result turf quality declines and sports fields provide less cushioning for players. Turf shows less stress tolerance and increased susceptibility to weeds, disease and insect problems.

Although these two conditions are basically unrelated and often not seen together in the same area of turf, each can be remedied by periodic aeration followed by topdressing with a variety of materials.

Aeration opens channels in the soil through which air, water and nutrients can move more freely. Aeration increases pore space, softening hard soil by allowing it to move upon impact. When a topdressing is applied and dragged in after aeration, the channels are filled with the loose material and will not be as likely to collapse or otherwise close back up. This preserves the benefits of aeration and maintains the soil in a favorable condition for a longer period of time. In filling the holes with a loose, rich topdressing, a favorable environment is created for the growth of bacteria and fungal organisms responsible for the natural decomposition of thatch. The newly filled channels also provide a favorable medium for the growth of new roots and a deeper root system. As long as these conditions persist, the excess build up of thatch will not become a problem. Periodic soil cultivation of this type insures a healthy, vigorous turf.

Degree of soil compaction varies with soil texture, mixture content, area use and amount of weight applied. Soils high in silt and clay compact more quickly than sandy soils; wet soils compact more quickly than dry soils. Most soil compaction occurs within the top 1 to 3 inches of the soil surface from normal use but may also result from heavy equipment traffic or repeated aeration to the same depth.

Check for soil compaction by using a soil probe, shovel, blunt rod or screwdriver.

Consider your aeration alternatives based on the hardness of your soil, weather conditions, turf growth cycles and field-use schedules.

Proper soil moisture enhances aeration effects. Dry soils are hard to penetrate, limiting the effect of the procedure and stressing equipment. Wet soils may not move enough to achieve satisfactory results. Generally, soil moistures should be at field capacity when you aerate. For vibrating and shattering aerators, the soil should be slightly drier. Field capacity generally exists 24 hours after a rain or irrigation. Hot, dry weather and strong winds may dry out the turf bordering aeration holes. Therefore, avoid aeration during such conditions or compensate for moisture loss with irrigation.

Shallow aeration reaches into the top 3 or 4 inches of soil. Equipment using solid spikes poke holes in the soil, creating openings without removing soil. Equipment with hollow tines or spoons removes soil cores and deposits them on the soil surface. In most cases, hollow tines or spoons are better. However, solid tine equipment that causes soil lifting and vibration can be quite effective. Using any equipment regularly at the same depth can cause development of a compacted layer. Deep aeration extends below the 4-inch level and helps improve both surface and deep-soil problems.

Ideally, aeration should reach the depth of compaction yet cause minimal surface disruptions. Equipment that brings solid cores to the surface is the most disruptive, but because it makes a greater change in existing conditions, it can produce the most long-lasting results.

Even when you drag cores back in, the turf needs time to recover and grass roots need to regenerate and spread deeper into the soil. Because spiking and slicing is less disruptive to turf growth and appearance, you can use it more often than coring. Spiking should not be the only method of aeration because it tends to compact the soil beneath each hole and will eventually lead to a layer of compacted soil at that level.

Consider using different types of cultivation at different times. Perform the more disruptive aeration on warm season turf in the spring before major root-growth periods. Shallow aeration before deep aeration should make both more effective. The most common and traditional method of core aeration involves using equipment containing hollow steel tines or open spoons.

Hollow tines use a vertical action to remove cores of soil. They force the tines to penetrate or "punch" holes in the soil surface to a depth of 3 to 6 inches. Larger units- called deep-tine aerators often offer optional cutting or spiking tools that can penetrate to greater depths, usually up to 12 inches.

In many cases, smaller units are self-powered, either walk-along or riding units. Others receive power from PTO systems from a tractor or other powered maintenance equipment. Larger units can be pull-behind types or three-point-hitch implements.

Open spoons are mounted to a roller, disc or barrel-type of equipment. The unit is then pulled or pushed across the area to be aerated. To avoid extreme surface damage, many of these units are equipped with spring-loaded, swivel or pivot assemblies on which the tines are attached to compensate for the rolling/pulling force as the tine enters and leaves the soil. Many of these units also have the capability of adapting to surface undulations over large areas to achieve successful results. Some units rely on gravity and the addition of heavy weights on the aerator to force the tines or spoons to penetrate the soil. Others use hydraulics to force down-pressure on the aeration unit to penetrate soil efficiently via a rolling action. Again, based on the type of cutting tool you use and the size of the aerator, soil penetration depth is typically between 3 and 12 inches.

As mentioned earlier, one of the major drawbacks of the traditional coring systems is the amount of surface damage encountered during the aeration process. Other potential problems include core-hole glazing and the creation of a hardpan layer. Glazing is the smoothing of the sidewall of the core hole that commonly occurs from aerating during wet soil conditions. When this happens, it actually seals off the plant root zone and causes more harm than good. Therefore it is important to avoid wet weather when using these types of aerators. Hardpan layers occur over time through repeated aeration applications with the same equipment at the same depth, creating a compacted soil layer just below the aerated level.

Aerators that do not remove the cores, such as solid-tine spiking and slicing, are similar to traditional coring and spooning equipment. In fact, it is becoming more common for manufacturers to offer equipment that allows for quick-and-easy interchanging of a variety of cutting or spiking tools. Other companies offer specialized equipment that perform a specific soil-cultivation task.

Alternative techniques are a recent trend. A few of the more recent developments in turf aeration include deep-tine coring, spiking or drilling; water-injection systems; and soil-shattering units.

Deep-tine coring, spiking or drilling has gained great popularity over the past few decades. By penetrating deeper into the soil profile, you encourage the benefits gained from traditional aeration but at a greater depth. Certain equipment offers options for soil penetration up to 24 inches. You do need to take special care when using deep-tine equipment to avoid damaging underground utilities, drainage and irrigation systems. Some of the more positive results from deep-tine aeration include the breaking up of soil layering caused by inconsistent top-dressing practices, as well as breaking through hardpan layers created by traditional 4-inch coring. In addition, some units offer the process of fracturing the core sidewalls to avoid core-hole glazing. Deep-tine aeration also is beneficial in managing the black layer. Deep-soil penetration allows the release of phytotoxic gases, improves soil-water drainage and improves surface-water and nutrient infiltration.

Water-injection systems, the newest option to turf-aeration, also are becoming quite popular. They force small streams of water through a high-pressure system to deeply penetrate the soil and break up compaction or treat localized dry spots without disrupting the surface area. You also can use them to incorporate certain liquid soil amendments, such as wetting agents or fertilizers. The greatest advantage of water-injection systems is that you can use them throughout the season during heat or dry stress periods when traditional aerators would cause severe turf damage.

Some of the limitations of water-injection systems include the lack of soil/thatch removal and not effectively gauging the depth of water penetration into the soil profile. Although these units are versatile and you can use them for many turf applications, they seem to have found a permanent home on golf courses and athletic-field complexes, where it is vital to limit disruption of play and field availability.

Soil-shattering units use a unique design where solid tines are forged using a combination of angles at various points on the tines. Then the tines are mounted onto a barrel-type frame and used as a pull-behind or 3-point-hitch unit. When in use, these units penetrate about 7 inches deep and create a twisting action that shatters the soil in a sideways and downward direction. Turf surfaces experience very little damage, and you can accomplish cleanup by performing a couple of mowings in opposite directions. These units are designed specifically for use on golf-course fairways, roughs, parks and sports complexes.

Purchasing considerations

Before purchasing a new-or even a used-turf-aerator system, it is important that you evaluate your operation and match the equipment to your budget and needs. For example, aerating a home lawn may not demand the precision in core spacing or depth that a golf-course putting green requires. In fact, equipment companies actually offer turf-aerators that are primarily designed for use on putting greens. Some are walk-behind units, some are riders, and you can mount some on small tractors. Many offer a range of choices for tine or spike diameters from 0.25 to 0.75 inch. Other features include various cutting-tool depths and applications and adjustable core spacing.

A few manufacturers have designed models for commercial use by lawn-care companies with golf-course-type features. These units can withstand the demands of home-lawn or grounds-maintenance use. However, these units do not provide the precision of hole-spacing and quality that is demanded for a golf-course putting green. Even though somewhat heavier and built to withstand hitting rocks and tree roots-not typically found on a putting green-these aeration units have fewer moving parts and contain less manufacturing and engineering costs. Thus, they typically cost much less than the golf-course models.

Sizing an aerator unit is important to consider before purchasing. Keep in mind whether your needs may require an aerator for use in small areas with obstacles such as trees, sidewalks and landscaped beds. Thus, you need to match equipment to fit those needs. You also must be able to maneuver the unit in a safe and efficient manner while achieving your aeration goals.

At the opposite end of the spectrum, if you aerate large turf areas--such as golf--course fairways or athletic fields-you may need a larger unit that will cover the area in a shorter time. Some of these units also are capable of maneuvering around obstacles while also operating in a more open area.

Still, another factor to consider is that lawn-care companies use aerator units more often and in more types of locations than a user such as a sports-field manager, who is responsible for only one location. If you operate a lawn-care company, then, you may need to purchase more than one unit. Even on single sites such as golf courses, however, it has become popular to purchase multiple units to complete the aeration task on putting greens and tees in a shorter time to limit the disruption of play.

In numerous cases, grounds professionals use a combination of aerating systems. In some instances, for example, superintendents practice traditional aeration as many as two to three times per season. They then may supplement this technique with deep-tine or water-injection aeration to achieve desired results. Costs involved in deep-tining or water injection are somewhat greater, and the jobs themselves also are more complicated. In certain cases, you may want to consider contracting these operations out to a qualified contractor.


Generally, the longer aeration holes remain open to the hot surface, the longer lasting the effect. A sealed hole, even if only at the surface significantly reduces air and water benefits. Topdressing with a porous material, sand or a coarse-textured soil, keeps the holes open. Repeated topdressing over a long period, especially in conjunction with aeration, provides other benefits. Topdressing can improve the soil profile, provide protection for turf seed and young plants, protect the crowns of existing turf, improve drainage, help decompose thatch and aid in leveling uneven surfaces.

Topdressing programs vary according to the changes you desire, soil profile, type and condition of the turf, degree of compaction, turf growth cycles, weather condition and use.

Generally, it's best to match the texture of the topdressing material with that of the existing soil to avoid layering. Topdressing with sand is common on golf-course greens because greens are about 90 percent sand. However, unless you are committed to two or more topdressings for 3 or more years, or have a field of sandy soil, sand may not be the best bet for a general sports field. Mixing a small amount of sand may worsen soil conditions, not improve them. Other alternatives are finely screened compost and ground up synthetic rubber tires (crumb rubber) has recently been used on some athletic fields on the Mainland. The simplest approach is to allow aeration soil cores to dry, and then drag them back over the turf as the topdressing material.

When you need additional topdressing material, the rate or thickness of application will vary, depending on time and budget, playing season and growing season or weather conditions, and whether core aeration has preceded topdressing. In any case, care should be taken not to apply too much at one time.

Calibrate your spreader

Inconsistencies in materials or application thickness may create layering of different textures and may hamper, rather than improve, air, water and nutrient movement.

To avoid these problems, calculate the rate of application precisely and calibrate equipment carefully for uniformity. A 0.125-inch layer of topdressing is 10.5 cubic feet or 0.4 cubic yard per 1,000 square feet. Topdressing a baseball infield of 17,000 square feet takes one-third the time and material that topdressing a 57,600 square feet football field does.

Most cultural practices, including topdressing, reduce turf quality and growth temporarily. The combination of aeration and topdressing will cause greater stress than either alone. However, fertilizing a week or two before cultivation can increase recovery rate.

Aeration and topdressing make a major impact in your overall turf grass management program because the turf root mass is concentrated in the upper 6 to 8 inches of the soil profile, where these practices most improve soil conditions.


Tips for sports turf managers, Gil Landry, Univ of Georga, in Grounds Maintenance, August, 1997.
Aeration spells relief for compacted turf, David A. Willoughby, in Grounds Maintenance.
Is soil compaction killing your field? Gil Landry, Univ of Georga, in Southwest Trees and Turf, May, 1999.
Crumb rubber benefits trafficked turf, J.T. Vanini, et. al.,in Golf Course Management, April, 1999.

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Jay Deputy, deputy@hawaii.edu, and Paul Murakami, pmurakam@hawaii.edu
Education Specialists, CTAHR

Slugs and snails are a major pest of our nursery and landscape industry as well as for the homeowner. They are able to completely destroy plants in one night if populations are high. Normally they prefer to consume herbaceous plants and have been know to traverse quite a distance up woody stems or limbs in order to eat the more succulent leaves or flowers of a plant. Snails and slugs feed on a variety of living plants as well as on decaying plant matter. They appear to adapt to whatever fare is available with a large host range of plants now under attack by these pests. The use of a mulch layer to conserve moisture and nutrients has given rise to a perfect environment to hide and multiply. Although they are not known to carry many diseases they greatly affect the quality of the plants in the garden, nursery or landscape. There are many species of introduced snails and slugs to Hawaii and they are competing with our endemic or native snail populations. These exotic varieties are displacing some of our native species by competition for available food and territory.

According to CTAHR Extension Urban Entomologist Julian Yates, there are nine varieties of slugs and about two dozen land and freshwater snails reported in the Hawaiian Islands. Yates says the most commonly asked about slugs are Vaginulus plebeia (Fisher), Veronicella cubensis (Pfeiffer) and the black slug, Veronicella leydigi (Simroth). In addition to the slugs, the pestiferous snails that are often encountered in residential flower beds, vegetable gardens, and commercial farms include the Giant African snail, Achatina fulica (Bowdich), Small Garden snail, Bradybeana similaris (Ferussac), and the brown garden snail, Helix aspersa (Muller), which was introduced into California in the 1850s for use as food and has since found its way to our Islands.

Snails and slugs move by gliding along on a muscular "foot." This muscle constantly secretes mucus, which later dries to form the silvery "slime trail" that signals the presence of these pests. Adult brown garden snails lay about 80 spherical, pearly white eggs at a time into a hole in the topsoil. They may lay eggs up to six times a year. It takes about 2 years for snails to mature. Slugs reach maturity in about a year.

Snails and slugs are most active at night and on cloudy or foggy days. On sunny days they seek hiding places out of the heat and sun; often the only clues to their presence are their silvery trails and plant damage. In mild-winter areas such as in Hawaii, young snails and slugs are active throughout the year.

During colder weather, snails and slugs hibernate in the topsoil. During hot, dry periods, snails seal themselves off with a parchmentlike membrane and often attach themselves to tree trunks, fences, or walls.

Pest management

A good snail and slug management program relies on a combination of methods. The first step is to eliminate, to the extent possible, all places where snails or slugs can hide during the day. Boards, stones, debris, weedy areas around tree trunks, leafy branches growing close to the ground, and dense ground covers such as ivy are ideal sheltering spots. There will be shelters that are not possible to eliminate--e.g., low ledges on fences, the undersides of wooden decks, and water meter boxes. Make a regular practice of removing snails and slugs in these areas. Also, locate vegetable gardens or susceptible plants as far away as possible from these areas. Reducing hiding places allows fewer snails and slugs to survive. The survivors congregate in the remaining shelters, where they can more easily be located and controlled. Also, switching from sprinkler irrigation to drip irrigation will reduce humidity and moist surfaces, making the habitat less favorable for these pests.


Handpicking can be very effective if done thoroughly on a regular basis. At first it should be done daily; after the population has noticeably declined, a weekly handpicking may be sufficient. To draw out snails, water the infested area in the late afternoon. After dark, search them out using a flashlight, pick them up (rubber gloves are handy when slugs are involved), place them in a plastic bag, and dispose of them in the trash; or they can be put in a bucket with soapy water and then disposed of in your compost pile. Alternatively, captured snails and slugs can be crushed and left in the garden.


Snails and slugs can be trapped under boards or flower pots positioned throughout the garden and landscape. You can make traps from 12" x 15" boards (or any easy-to-handle size) raised off the ground by 1-inch runners. The runners make it easy for the pests to crawl underneath. Scrape off the accumulated snails and slugs daily and destroy them. Crushing is the most common method of destruction. Do not use salt to destroy snails and slugs; it will increase soil salinity. Beer-baited traps have been used to trap and drown slugs and snails; however, they attract slugs and snails within an area of only a few feet, and must be refilled every few days to keep the level deep enough to drown the mollusks. If using beer, it is more effective fresh than flat. Traps must have vertical sides to keep the snails and slugs from crawling out. Snail and slug traps can also be purchased at garden supply stores.


Several types of barriers will keep snails and slugs out of planting beds. The easiest to maintain are those made with copper flashing and screens. Copper barriers are effective because it is thought that the copper reacts with the slime that the snail or slug secretes, causing a flow of electricity. Vertical copper screens can be erected around planting beds. The screen should be 6 inches tall and buried several inches below the soil to prevent slugs from crawling beneath the soil. Copper foil (for example, Snail-Barr) can be wrapped around planting boxes, headers, or trunks to repel snails for several years. When banding trunks, wrap the copper foil around the trunk, tab side down, and cut it to allow an 8-inch overlap. Attach one end or the middle of the band to the trunk with one staple oriented parallel to the trunk. Overlap and fasten the ends with one or two large paper clips to allow the copper band to slide as the trunk grows. Bend the tabs out at a 90 degree angle from the trunk. The bands need to be cleaned occasionally. When using copper bands on planter boxes, be sure the soil within the boxes is snail-free before applying bands. If it is not, handpick the snails and slugs from the soil after applying the band until the box is free of these pests.

Instead of copper bands, Bordeaux mixture (a copper sulfate and hydrated lime mixture) can be brushed on trunks to repel snails. One treatment should last about a year. Adding a commercial spreader may increase the persistence of Bordeaux mixture through two seasons. Sticky material (such as Stickem Green, which contains copper) applied to trunks excludes snails, slugs, ants, and flightless species of weevils.

Barriers of dry ashes or diatomaceous earth heaped in a band 1 inch high and 3 inches wide around the garden have also been shown to be effective. However, these barriers lose their effectiveness after becoming damp and are therefore difficult to maintain.

Natural Enemies

Snails and slugs have many natural enemies, including ground beetles, pathogens, snakes, toads, turtles, and birds (including ducks, geese, and chickens), but they are rarely effective enough to provide satisfactory control in the garden. A predaceous snail, the decollate snail (Rumina decollata), has been released in southern California citrus orchards for control of the brown garden snail and is providing very effective biological control. It feeds only on small snails, not full-sized ones. Because of the potential impact of the decollate snail on certain endangered mollusk species, it cannot be released outside of a 12-county area in California. Also, decollate snails may feed on seedlings, small plants and flowers as well as be a nuisance when they cover the back patio on a misty day.


Snail and slug baits can be effective when used properly in conjunction with a cultural program incorporating the other methods discussed above. Baits will kill decollate snails if they are present.

Metaldehyde or metaldehyde/carbaryl snail baits can be hazardous and should not be used where children and pets cannot be kept away from them. A recently registered snail and slug bait, iron phosphate (Sluggo or Escar-Go), has the advantage of being safe for use around domestic animals and wildlife.

Never pile bait in mounds or clumps, especially those baits that are hazardous, because piling makes a bait attractive to pets and children. Placement of the bait in a commercial bait trap reduces hazards to pets and children and can protect baits from moisture, but may also reduce their effectiveness. Thick liquid baits may persist better under conditions of rain and sprinklers.

The timing of any baiting is critical; baiting is less effective during very hot, very dry, or cold times of the year because snails and slugs are less active during these periods. Irrigate before applying a bait to promote snail activity. Make spot applications instead of widespread applications. Apply bait in a narrow strip around sprinklers or in other moist and protected locations or scatter it along areas that snails and slugs cross to get from sheltered areas to the garden.

Ingestion of the iron phosphate bait, even in small amounts, will cause snails and slugs to cease feeding, although it may take several days for the snails to die. Iron phosphate bait can be scattered on lawns or on the soil around any vegetables, ornamentals, or fruit trees to be protected. It breaks down less rapidly than metaldehyde and may remain effective for several weeks, even after irrigation.

Avoid getting metaldehyde bait on plants, especially vegetables. Baits containing only metaldehyde are reliable when conditions are dry and hot or following a rain when snails and slugs are active. Metaldehyde does not kill snails and slugs directly unless they eat a substantial amount of it; rather, it stimulates their mucous-producing cells to overproduce mucous in an attempt to detoxify the bait. The cells eventually fail and the snail dies. When it is sunny or hot, they die from desiccation. If it is cool and wet, they may recover if they ingest a sublethal dose. Do not water heavily for at least 3 or 4 days after bait placement; watering will reduce effectiveness and snails may recover from metaldehyde poisoning if high moisture conditions occur. Metaldehyde breaks down rapidly when exposed to sunlight; however, Deadline, a special formulation of metaldehyde, does not. Deadline holds up well in wet weather and does not have the problem with sublethal doses that other metaldehyde baits have.


Snails and Slugs, John Karlik,UC-DANR Publication 7427.
Slugs and Snails, Julian Yates, University of Hawaii.

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Jay Deputy, deputy@hawaii.edu
Education Specialist, CTAHR

Iron (Fe) deficiency affects a number of popular landscape plants in Hawaii. These include citrus, heliconia, hibiscus, bauhinia (Orchid Tree), bougainvillea, allamanda, gardenia, centipedegrss, and many others.

Iron is an immobile nutrient and is not moved from old growth to new growth to compensate for diminished supply. Therefore, iron deficiency symptoms appear on new growth. The most common and prominent symptom is interveinal chlorosis (yellowing) on young leaves, with the larger veins remaining green. Leaves may scorch as the severity of iron deficiency increases, and if very severe, iron deficiency leads to reduced growth and shoot dieback.

Iron deficiencies are sometimes difficult to diagnose and the symptoms are often confused with a manganese (Mn) deficiency. Both result in interveinal chlorosis and appear under the same environmental conditions. In some cases, a Mn deficiency will include interveinal yellowing, but in this case the smallest veins remain green. The second difficulty in establishing an iron deficiency is that a tissue analysis by a laboratory will more than likely report the results in total iron and not available iron. It is well documented that total iron values do not often correlate with an actual iron deficiency. So therefore, be careful in your diagnosis of the problem. A quick and dirty approach to help in the diagnosis of a suspected iron deficiency is to spray a few leaves with a ferrous sulfate or iron chelate solution. However, lack of a response does not in itself mean you do not have an iron problem. Iron deficiency most frequently results from high soil pH. It may also be induced by cold wet soils, compacted soils, and excessive Zn, PO4, or Mn.

Several corrective approaches for iron deficiency have been used been successful for trees and some palms. These include

  • Ferrous sulfate, sold as Inject-A-Min" Iron-Zinc, Microject (1.4% Fe) by J.J. Mauget Co;

  • FeEDTA and ferric ammonium citrate sold as Iron-Zinc Stemix" (1.0% Fe) by J.Mauget;

  • Ferrous sulfate from Medi-Ject Tree Injection Systems, Inc.

  • Ferric ammonium citrate sold as Complete Green" (8% Fe), Complete Green Co, (Fe-citrate has been suggested as the form of iron transported in the xylem from the roots to shoots.)

There has been considerable discussion about the potential negative impact of the wounds caused by trunk injection methods. Minimizing the hole diameter and number of holes is an important consideration.

Iron is also inserted in solid form into trunks. Medicap Fe from Creative Sales, Fremont, Nebraska, contains 28% ferric ammonium citrate.

Foliar spray applications are generally less effective in producing a long-term response. Since iron is not mobile, treatments must be repeatedly applied to new foliage as it develops. Use a 0.5% solution of iron sulfate (20% iron) with a spreader-sticker. Avoid spraying in very hot weather. Additional foliar sprays include urea/iron sulfate sold as FeRROMEC" liquid iron (15-0-0, 6% Fe), and several chelated iron formulations including Sequestrene" Fe138 (6% Fe as FeEDDHA), SequestreneR Fe330 (10% Fe as FeDTPA), and Fe lignosulfonate which is the least effective.

Acidifying materials can solve landscape pH problems, but they should not be used on a large scale unless you are amending planting beds prior to planting. Elemental sulfur is effective and has a reasonable buffer period. The amount required depends on initial pH, the extent of pH change required, and particle size of sulfur (fine particles are faster). One study found that 20 lb./100 square feet was required to drop pH from 8.2 to 6.6 in 7 months. This is a very large amount. Never apply more than 5 pounds per 1000 square feet per application if turf or other plants are present. Aluminum sulfate provides a more rapid change in pH than sulfur, however, the duration is not as long. Since aluminum toxicity is a problem in some Hawaiian soils, a soil analysis should be run before applying this product.

Several different iron compounds may be applied as soil amendments, but are not effective in established landscapes unless very high rates are used. Ferrous sulfate (FeSO4) contains 20% iron and is sometimes used as a soil application, and will also lower soil pH. Ferrous ammonium sulfate contains 14% iron, is more expensive, and also lowers soil pH somewhat. Iron chelates containing 5% to 14% Fe can also be used as soil additives, but are also expensive. At high rates the chelated iron compounds have the potential for chelating other cations (Mn, Zn). Two of the more effective chelated iron compounds are FeEDTA , most effective on acid soils, and FeEDDHA which is effective over a wider pH range. Fritted micronutrients (commonly a component in fertilizers) are another possibility, but are more appropriate for maintenance programs than for correcting deficiencies. Organic complexes such as Fehumate (Vigoro Industries), used at 40 to 100 gm Fe/tree, or 0.5 to 1.0 lbs Fe/1,000 square feet are cost-effective slow-release sources of iron.

A few recommended cultural practices to minimize the problem include avoiding over-irrigation and nutrient imbalances such as excess P or micronutrients (especially Mn and Zn). For dicots, avoid fertilizers with large amounts of nitrate. This is less effective for palms, grasses, etc. Avoid damaging roots and circumstances that tend to compact soils (e.g. construction traffic) Potassium (K+) salts and ammonium (NH4) forms of nitrogen generally improve an iron deficiency situation.

Adapted from an article by Dr. James A. Robbins, Director of Horticultural Research, IMC Vigoro.

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Jay Deputy, deputy@hawaii.edu
Education Specialist, CTAHR

There are many misconceptions about trees and their care that have been innocently passed along without much critical evaluation. This article attempts to correct some of the more common mistakes and misconceptions, putting them into the proper perspective with regard to recent research findings.

A tree's root system is not the mirror image of its aboveground portion.

Since studies on tree-root structure began back in the 1930s, researchers have found that, regardless of species, climate or geographic location, most tree roots consistently grow shallow and wide. The lateral roots spread out to occupy an area that is 1 1/2 to 4 times the width of the canopy and are usually within the top 3 feet of soil. Roots on trees and shrubs planted in a landscape grow more rapidly than the tops, reaching to 3 times the branch spread within 2 or 3 years after planting. The finer roots are concentrated in the top several inches of soil and are subject to minor soil disturbances, which can injure or remove a large portion of the absorbing roots on a tree or scrub. This often happens in landscapes surrounding recently constructed buildings.

As soil depth increases, root growth diminishes, primarily due to a decrease in oxygen and moisture levels. The depth, spread and degree of branching, however, are greatly influenced by factors such as soil texture (relative proportion of sand, silt and clay), the degree of aggregation of soil particles creating pore spaces, soil fertility and available moisture. Few roots grow deeper than five feet, although some can be found at much greater depths in areas with deep, course soils or in gravel veins or fractured rocks.

In sandy, well drained soils some trees such as ironwoods and pines develop deep taproots directly beneath the trunk. However, most trees do not have taproots. When the water table is close to the soil surface or when the soil is compacted, taproots do not develop. Taproots generally do not form on trees planted in our urban landscapes.

A large, deep planting hole is detrimental to a newly transplanted tree or shrub.

A common practice is to dig a large, deep hole to accommodate root development. These holes can be as large as 5 feet wide and just as deep. Yet, a tree's naturally shallow and wide root system makes this approach a detriment to tree establishment. The root ball should never be covered any deeper than the top of the native soil around its base. Soil dug out and amended with organic matter, or even just spaded up and loosened below the root ball, settles after planting. As the root ball sinks, soil covers the roots and trunk base, eventually inhibiting or preventing water from entering the root ball. As little as a half-inch of excess soil around the base of the tree can cause this problem.

Other serious problems can slowly develop when soil comes into contact with root collar phloem tissue. The root collar is the junction of the roots and trunk, characterized by the flare of major lateral roots. The root collar is part of the trunk and is therefore not specialized to resist constant soil moisture. Continuous moisture restricts gas exchange between the atmosphere and phloem tissue of the root collar, causing the phloem tissue to gradually die. As a result, the tree becomes susceptible to crown rots and pathogens such as Phytophthora.

To prevent these problems, dig holes no deeper than the root ball height, the National Arborist Assoc. recommends a planting hole 1 to 3 inches shallower than the root ball. Thus, the root ball is set on undisturbed soil that does not settle. The tree should be planted so that the root flare is visible and above ground. Because lateral roots are wide spreading, dig the hole three to five times wider than the diameter of the root ball. Roots grow more quickly into loosened soil than compact soil, thus speeding up the tree's establishment period.

The root ball of some trees is wrapped in burlap immediately after being dug up. This is to keep the root ball in one piece and to reduce moisture loss. Carrying a balled and burlaped tree by the trunk without supporting the root ball can seriously injure the root system. When planting, set the root ball in the hole, position the tree, then remove the twine and nails at the top of the ball. Remove or fold back burlap from the upper third of the root ball. The burlap will be penetrated by newly established roots and eventually decompose.

Root pruning does not stimulate new root growth all the way back to the trunk.

Roots are often pruned before moving a tree in hopes of creating a denser root ball. However most root growth after root pruning takes place just behind the root pruning cut, not further back toward the trunk. Therefore, dig the root ball of a recently root pruned tree several inches beyond the point of the root pruning. Root pruning should be conducted 6 to 10 weeks before moving the tree. Root pruning more than 10 weeks before moving the tree may reduce the advantages of pruning, because regenerated roots will quickly grow outside of the intended root ball area.

Roots circling around a container do not continue to grow in a circle once the tree is planted in the landscape. Roots frequently circle within the perimeter of a container several times before the tree is planted into the landscape. The portion of the root that grew in the container does not straighten out, but new growth on this root will not continue to circle. If the root ball is seriously pot-bound with these circling roots, it is best to prune the excess outer roots to promote new root growth. Root pruning in this case can cut up to 50% of the roots in container trees but this is sufficient to permit plant establishment. Always remove the container prior to planting.

As was stated before, plants should be transplanted no deeper in landscape soil than they were in the nursery. Trees and shrubs should be planted at the same depth or slightly shallower than they were in the nursery field soil or container medium. This allows for the quickest root growth which is crucial to tree and shrub establishment. Planting too deep slows root growth, which can lead to poor establishment or death.

Hardpan layers in the soil should not be removed at the time of planting to accommodate the root ball.

Hardpans, which are cemented or heavily compacted layers of soil, are a common obstruction to planting and oftentimes landscapers remove them. A hardpan may typically be formed as a result of soil compaction due to construction or heavy traffic, or naturally produced by soil particles cemented together with calcium carbonate. A hardpan can be found at or within a few inches the soil surface, or several feet below. These hardpans can be as hard as concrete and as thick as a few inches to a few feet. The standard practice has been to use a pickax, crowbar or even a jackhammer to remove the hardpan, especially layers that are several feet deep. Yet, removing this hardpan is completely unnecessary. Even relatively shallow layers can be left in place. Generally, these layers are not solid or continuous, but fractured, so water is able to drain through. In arid regions, many native trees grow successfully over these layers very close to the soil surface. Excavations of mesquite trees growing on hardpan show the trees' ability to root over and even through it.

Trees can be planted without removing the hardpan as long as there are several inches of overlaying soil. Smaller root balls must be planted where hardpans are close to the soil surface. The same mounding technique that is employed on poorly drained soils or those with high water tables can be used for planting over hardpans.

As with standard planting recommendations, the root ball should be set on undisturbed soil, in this case, the hardpan itself. Soil is then bermed up to cover the portion of the root ball that extends aboveground. If the hardpan is solid and does not drain, then a drainage column can be dug through the hardpan. Do not dig under the root ball, but to its side. This funnels water away from the root ball base and reduces the danger of roots becoming waterlogged.

Organically amending the backfill of planting holes does not promote faster or healthier root growth.

During the past 15 years, many studies have been conducted on whether organic soil amendments, such as peat, compost and bark, added to the backfill helps plant growth. In most cases, they inhibited top and root growth. When used in a deep planting hole, organic amendments gradually lead to the root ball sinking below the level of the surrounding native soil. Organic matter shrinks significantly as it decomposes, causing the root ball to settle. Using organic amendments in the backfill leads to other plant problems, due to the incompatibility of different soil types. When trees are planted, these soil types, or interfaces, inevitably come into contact with each other. Whether the plant was field- or container-grown, the root ball soil is almost always different from the backfill soil at the planting site. Roots have difficulty penetrating this foreign soil. When backfill soil is organically amended, an additional interface is added, making root penetration even more difficult. Circling roots and unsuccessful plant establishment can result.

To minimize these problems, backfill holes with the same soil taken from the hole. Do not incorporate any organic amendments into the backfill, even if soil conditions on the planting site are poor. For long-term survival, trees must be able to establish roots in the existing soil conditions. For the most effective and quickest root establishment, loosen or till the soil to the root ball's depth in a circular area three to five times greater than the diameter of the root ball and mix in a starter fertilizer high in phosphorus. The National Arborist Association does not recommend fertilizing at time of planting, but my opinion is that planting is the best time to incorporate phosphorus into the root zone since it is not a mobile nutrient. After transplanting, apply a layer of mulch 2-3 inches deep over the entire area that was tilled, leaving several inches free of mulch around the base of each plant.

Top-pruning at the time of transplanting does not reduce transplant shock or improve establishment.

Numerous studies on container-grown and bare-root plants have shown that removing buds and young leaves at the time of transplanting actually reduces root initiation and growth. This is because such pruning reduces photosynthesis and the sugars and carbohydrates necessary for root growth. For most plants, buds and young leaves produce compounds that stimulate root initiation and growth. Removing top growth reduces the tree's ability to manufacture these compounds, which are necessary for new root development. Pruning does stimulate growth of individual branches, but it has an overall dwarfing effect on the plant. The National Arborist Association recommends pruning at the time of planting only to remove broken, damaged, diseased or dead branches. Begin corrective pruning after the tree has become well established, usually 1 to 3 years after planting.

Pruning paint does not repel water and promote rapid closure of wounds, but rather may promote decay and disease-causing organisms.

The practice of applying pruning paints, or wound dressings, continues to this day even though research has shown that these products have no value. Pruning paint does not seal off the wound and protect the tree from cracks, mushrooms, wood rot and disease-causing organisms. In fact, pruning paint encourages them. When exposed to the sun, the wound dressing often cracks, allowing moisture to enter and accumulate in pockets between the wood and paint. This provides a perfect environment for diseases to develop. In addition, if pruning equipment, such as shears or saws, are contaminated with a disease organism like sooty mold or slime flux, the dressing can seal the organism against the wound. Asphalt-based wound dressings can also be phytotoxic. Some growers and landscapers believe that pruning paint is unnecessary on small cuts, but it should be used on any wound larger than 1 inch in diameter. However, pruning paint should not be used regardless of the size of the cut. Plants must seal off the injured tissue from the healthy portion of the plant in order to stay alive. The swollen callus tissue developing around a trunk wound or pruning scar is closing over the injured tissue, not healing it. Properly made pruning cuts successfully callus much more rapidly if left unsealed.

Branches that are cut off flush with the trunk inhibit closing of wounds and can lead to decay.

Much of the pruning done today does not take into account the importance of the branch bark collar, which is the point at which the branch joins the trunk. Usually this area appears as a distinct swelling at the base of the branch, although the swelling is not too noticeable in some species. The branch bark collar contains chemicals that help protect the tree from the spread of disease organisms and decay. When cuts are made flush with the trunk, these chemicals are lost. Even worse, this kind of pruning can lead to the cutting of trunk tissue, which makes wound callusing difficult, if not impossible.

Never make cuts flush with the trunk. Cuts should always be made just to the outside edge of the swollen branch bark collar region. Thus, the branch bark collar remains intact, only branch tissue is cut, and the trunk is not damaged.

Rapid thick callus growth around a pruned branch does not indicate the branch was pruned properly. The callus forming around a pruning scar often forms rapidly, regardless of the pruning technique. This tissue should form a ring or donut-shape if the branch was removed properly. If the callus is elongated or oval-shaped, the branch was pruned too close to the trunk. Despite rapid callus formation around a pruning cut or injury, extensive wood rot can develop inside the tree.

Injury caused by heavy equipment during construction, or at any other time, can cause major injury to a tree.

Trees cannot replace injured tissue, therefore even a small trunk wound can permanently reduce the trees capacity to fight future stress caused by insects, disease or other factors.

Many roots are destroyed as heavy equipment operates over the root system. Even one pass over the root system with a bulldozer, earth scraper or other piece of heavy equipment can cause significant root damage. Damaging roots on one side of a tree may cause branch dieback on that side only, or at random throughout the crown.

To save a tree during construction, do not disturb soil beneath the branch drip line at the very minimum. Tree roots extend to 3 or more times the drip line of the tree. Approximately 50% of the root system is located inside of the drip line. No equipment should operate within this area if the tree is to be saved. Sturdy fences should be constructed at the drip line to encourage enforcement of this guideline. This serves as the best guide to helping prevent construction related tree decline. Grading to prepare a site for laying sod or planting shrubs can harm trees. Since many of the fine roots are located close to the soil surface, changing the soil grade by as little as 6 inches can cause extensive damage to the root system of existing trees. Design the landscape to largely fit the existing grade. If grade changes are necessary close to a tree, remove the tree and plant several younger, healthy trees.

Never remove soil from or add soil to the area within the drip line of a tree that is to be saved. Building a wall which is commonly called a "tree well" several feet from the trunk and adding more than 3 or 4 inches of soil to the area outside of the well can kill the tree. If a tree well is to be used, construct it no closer to the tree than the drip line and grade the soil outside of the well to prevent runoff water from entering the well. There have been reported cases of success using a system of gravel spread over the existing grade. Vertical vent pipes are installed every 10 ft. to supply the roots with oxygen. Coarse textured fill soil is then carefully spread over a soil-separator fabric placed over the gravel.

If a tree survives the first 2-4 years following construction it may still die from construction related injuries. Trees frequently decline after construction of a building. Often, branches begin dying within a year or two due to severe root damage. The tree may be dead within 3 or 4 years. However, it is not uncommon for trees to show a slow decline over a 5 to 15-year period. The tree may not show obvious signs of decline for many years, but following a drought period branches may quickly loose leaves and begin a rapid decline. The tree may be dead a year or two later.

A tree trunk with a crook in it is just as strong as a straight one.

Trunks with slight doglegs, crooks or bends are not weaker than those that are straight. This is a normal development on many trees. Healthy trees will grow out of this condition and the trunk will appear straighter as it becomes larger in diameter.

Horizontally oriented branches are better attached to trees than upright branches. Upright branches are poorly attached to trunks. Horizontally oriented branches are usually well secured to trunks. A branch growing in an upright manner parallel to the trunk becomes a second trunk. The tree is said to have a double leader. Double leaders are dangerous because they can easily split from the tree during a storm. Never allow trees to grow with multiple upright leaders. These trees may look handsome when young but will become hazardous as they grow older. Always prune so that leaders or branches are spaced 18-36" apart along the main trunk and be sure they form an angle of more than 40° with the trunk.

Topping a tree creates a dangerous tree.

Topping or heading back is cutting branches or stems to random lengths, often resulting in the removal of most of the upper branches. Trees should never be topped. Topping creates hazardous trees because the wood inside the cut branch begins to decay. The sprouts that grow in response to topping are not well secured to the topped branch and they can easily split from the tree as they grow larger. To avoid this, always prune a branch back to a living branch crotch, leaving a leading branch for continued growth. This technique is called drop crotching.

Established trees do not usually need to be fertilized in order to maintain their health.

Established trees growing in a maintained landscape normally receive enough fertilizer for moderate growth because their root system grows into fertilized shrub beds and turf areas. In most instances, additional fertilizer is not necessary to maintain healthy trees. Some trees with micronutrient deficiencies respond to applications of minor elements.

If fertilization is necessary, tree fertilizer does not need to be injected into the soil. Tree roots grow among turf and shrub roots and most of the absorbing roots are located within the top 12-24" of soil. Fertilizer broadcast over the surface reaches tree, shrub and turf roots in adequate amounts. Established trees probably require less than 2 lbs. nitrogen/1000 sq. ft. of root area to maintain good growth, particularly if lawn clippings and leaves are recycled back into the landscape. A higher rate may promote rapid growth on young trees.

These are just some of the many prevailing tree-care considerations which have been enlightened by extensive scientific research. Those working in the green industry should be well informed, and help pass on this kind of information.


Pulp Fiction, John Begman (American Nurseryman, Nov 1, 1997).
Dispelling Misperceptions About Trees, Edward F. Gilman (Florida Cooperative Extension Service).
Please Don't Bury Me, Robert Rouse, National Arborist Association (WWW.natlarb.com).

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Jay Deputy, deputy@hawaii.edu
Education Specialist, CTAHR, and
Linda Cox,
Community Economic Development Specialist, CTAHR

With the continued economic growth and strong national housing market on the mainland, more than 21 million American households spent a record $16.8 billion on professional landscape/lawn care/tree services in 1998, according to a recent ANLA survey. This represents a $2.2 billion increase on total spending over the previous year and a 32% increase in the average amount spent by each individual household that uses these professional services.

Spending on landscape installation and construction accounted for the largest increase, both in total dollars spent nationwide ($6.3 billion) and average amount spent per household $2,630, (up 48%). Landscape maintenance accounted for the greatest share of the market with a total of $7.9 billion (up 4%). Total revenues from landscape design and tree care declined slightly.

The percentage and average cost per household for U.S. households using a professional landscaping service are shown in this table:

National homeowner landscape services in 1998.

Average cost per Service % home ($) Lawn/landscape maintenance 13.7 581 Landscape installation/construction 2 2630 Landscape design 1 742 Tree care 4 411

Twenty percent of American households used some type of landscape service in 1998.

The total percentage of households using a landscape service decreased, as compared to the 22% average over the previous five years, however individual households spent more for each service.

Due to Hawaii's dismal economic situation over the past several years, household spending in Hawaii for professional landscape services may not be as much as the US mainland. The most recent estimates of spending on landscape services in Hawaii are contained in the 1991 CTAHR publication, "An Economic Profile of Hawaii's Landscape Services" written by Linda Cox, Jim Hollyer and Don Schug. Using this data, the total gross sales for the landscape service industry in Hawaii can be adjusted for inflation up to May 2000, giving estimates for the current year. After making the adjustment, Hawaii's landscape architects are estimated to have gross sales of $11.9 million, and landscape contractors/maintenance are estimated to have gross sales of $298.1 million in the year 2000. Based on the 1991 survey, sales to private residential customers will account for 24% of the architects' gross sales ($2.85 million)and 42% of contractors' and maintenance firms gross sales ($125.2 million) this year. Annual in-house spending for landscape services by other industries such as hotels, golf courses, real estate management firms, government agencies, cemeteries, private parks, and private schools, is estimated to be $155.2 million this year. Thus, assuming spending patterns have remained the same as they were when the survey was conducted, annual spending on all landscape services is estimated to be $465.2 million for Hawaii this year.

The inflation adjustment is used to estimate the average annual cost for in-house landscape maintenance services for each user group in the table below.

Table 2.  Estimated landscape services cost in 
Hawaii for the year 2000.

Group                     Cost per acre        Total

Golf Courses                $5,922    $929,754 per course
Hotels                      14,505    130,545 per hotel
Real Estate Management Co.  1,584     72,864 per firm
Private Schools             6,060     109,080 per school
Cemeteries                  10,803    140,439 per cemetery
Private Parks               24,000    1,224,000 per park

(The spending for public parks is included in the 
estimates for government spending.)

The 1991 survey also estimated that the total number of full time employees in the landscape service industry and in landscape service positions in other industry sectors was 10,000 with an additional 1300 part-time worker. In 1989, before the decline of the sugar industry, total employment in landscape services was two times greater than the sugar industry and pineapple industry combined. While no information is available about landscape service employment today, these types of services are expected to be a large source of employment in agricultural occupations.

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Kayla L. McSwain
Former student, Horticulture, CTAHR

Golf course and resort grounds management has become more challenging with the increased use of reclaimed irrigation water. Reclaimed water, also called grey water, offers benefits in that it provides greater water availability where fresh water is limited. However, the problem of higher salinity usually complicates matters. High salt content of water can increase soil salinity, which may then increase soil compaction and reduce aeration, water infiltration and drainage. High water or soil salinity affects plants by reducing water uptake, causing wilt, burn and eventual death of susceptible plants. In light of these problems, salt-tolerant turfgrasses are now being recommended for golf course and resort developments where grey water irrigation is used. For the same reasons, salt tolerant trees and shrubs should also be a consideration.

Here in Hawaii, where some waters can be highly brackish, a few coastal shrubs accustomed to salt and salt sprays are being used in the landscape. Coconut palms, which are highly salt and wind tolerant, are also used with great frequency. However, to complete the landscape, small, attractive, salt-tolerant trees are also needed. This article suggests some possible species for consideration, as well as selection and cultural practices that will support this effort.

A great deal of study is being conducted worldwide on the subject of salt tolerance. Many phytophysiological mechanisms have been identified in plants which enable-salt tolerant plants to survive in saline conditions. Among these plant processes are ion pumping, salt secretion or storage, and succulence. The basic result of these mechanisms is the plant's ability to exude salts from foliar cells in order to maintain osmotic pressure and phytohormonal balances that enable growth. In order to compensate for higher salinity, plants must expend energy to produce and maintain these salt-blocking mechanisms. Often the result is reduced growth. Thus, salt tolerant plants are usually slower growing than less tolerant species. There are exceptions, however, and some plants appear to thrive in saline conditions.

It has been found that salt adaptation may be induced in some plants that were not previously known to be salt tolerant. Enhanced by the addition of ABA, salt adaptation has been observed by exposing plants to saline conditions. This adaptation has also been found to be transmittable to the next generation. Salt tolerance can also be reversed when plants are no longer exposed to saline conditions. Differences in tolerance levels often occur within the same species, so selecting for tolerance merely by species may not be completely satisfactory. Techniques are being studied for selection of salt-tolerant clones in early tissue culture and micro-propagation.

Various areas of research have sought to detect and enhance species tolerances. The increasing need for food is a major concern. Scientists are seeking to find and develop crops for desert and lands with salinity problems. Studies worldwide are using genotype selection, cultural practices, and biotechnology to develop more salt tolerant crops for food, fodder, and fuel for human use.

Re-vegetation is also an area of interest for salt-tolerant species. In Australia, for instance, extensive testing has been done to find large naturally occurring salt-tolerant trees for saline sites. Researchers in other studies have found justification for salt-tolerance selection in forest trees for forestation projects.

Because agriculture production is a major user of precious water resources, many studies are examining reclaimed water usage to supplement diminishing supplies. One cultural technique found to have some success in overcoming salinity problems is the selection of root stock and scion combinations in citrus grafting. Many other salt-tolerant orchard trees are being sought through this type of selection.

Salt tolerances of small trees

Selection of tolerant species is the simplest solution for landscaping of the golf courses and resorts. A listing of some possible tree species is found in the table on the next page. Wind is also an important factor on golf courses as trees are more exposed to wind than in other landscape situations. Thus, wind tolerances are also listed in the table. Normal growth rates and heights are listed, although it should be kept in mind that plant response to salinity often slows growth rates. For this reason, some taller trees are included in this table even though they are not usually considered to be small trees.

Taken from various (and sometimes conflicting) sources, this table is not meant to be an authoritative listing for guaranteed success. Testing is needed under field conditions to best determine the actual performance of each species. Soil salinity, soil compaction, poor drainage and flooding may also negatively affect plant health. Adequate rainfall and good drainage will afford better growing conditions. It should also be kept in mind that tolerances vary within the genotypes of each species, so selection from tissue culture may be appropriate.

Selection of salt tolerant genotypes, or forcing salt adaptation of moderately tolerant trees may also expand the variety of plant material. And as was found in citrus, rootstock and scion combinations may yield successful results. This type of selection may be more appropriately carried out by a nursery stock grower or research facility. The table lists some moderately tolerant species for consideration.

Another option would be to utilize some of the commonly grown shrubs, which can be easily trained into small trees. For slower growing species, transplantation of trained mature specimens may be required if a particular tree form is desired. A listing of shrubs that might be appropriate for this purpose also appears in the table.

Irrigation management for enhancing salt tolerance

Salt spray can be one of the most deleterious aspects of using brackish or gray water in irrigation. Avoidance of spraying tree canopies can enhance aesthetics and ultimately survival. Redesigning irrigation systems may be necessary in order to achieve this. In addition it is important to irrigate more heavily to allow soil salts to flush out of the root zone. Good drainage is vital to avoid puddling. Providing consistent moisture is also necessary to avoid concentration of the salts as the water evaporates. Fertilization must be managed carefully so trees will not become over stressed with even higher levels of salinity.

Of course, mixing clean, low-salinity water with brackish or gray water can also be a viable solution to lessen the amounts of salts in the water. Alternating between the fresh and reclaimed water will also help. One other alternative to lessen the damage by salt spray, is a system of fresh water spray irrigation after events of salt spray to effectively wash salts from leaf surfaces. This has been found to work in protecting park plants in Israel.


High soil and water salinity can be deleterious to the survival of sensitive plants. Several options to compensate for these effects are available. Selection and planting of salt-tolerant species is the easiest option. With field testing, more species may become more reliable and available for this purpose. The use of shrubs properly pruned to form small trees can also be a viable alternative. Irrigation and cultural practices offer alternatives in preventing salt damage. New technical propagation and selection techniques for the cloning of individual genotypes are becoming available through the advent of molecular biology.

Trees are a valuable asset to the golf course and resort landscape. With the increased use of brackish and effluent water for irrigation, the use of salt-tolerant species will become more important. Hopefully, these options may be helpful in achieving the overall goal of selecting healthy plant materials that are profitable and aesthetically pleasing for golf courses and resorts in Hawaii.

Table 1. Small Trees for Landscapes in Hawaii.

1. Good to excellent salt tolerance
Botanical name Common name Height Growth
Salt Wind Heat Comments
Euphorbia lactea Candleabra plant to 15' s E
Pandanus tectorius Hala, Screwpine 20-30' s-m E E Litter
Tournefortia argentea Beach heliotrope to 25' m-f E G
Bucida buceras Geometry tree 30' G
Cocothirax argentata Silver palm 20' G
Cordia sebestena Kou Haole, Geiger tree 20-30' s-m G G
Heritierra littoralis Looking glass tree to 25' s-m G M Litter
Hyophorbe lagenicaulis Bottle palm 10-15' s G
Mascarena spp. Bottle palm 10-15' G E
Phoenix reclinata Senegal date palm 25' G
Pittosporum crassifolium Karo 15-35' G G Tolerates alkaline soil
Prichardia thurstonii Masai, Thurston palm 15-30' s G
Sapindus saponaria Manele, Soapberry 10-30' G
Thrinax microcarpa Brittle thatch palm 15' G
Yucca aloifolia Spanish Bayonet 20' G

2. Moderate salt tolerance
Botanical name Common name Height Growth
Salt Wind Heat Comments
Caesalpinia pulcherrima Pride of Barbados 9-15' m-f FG E Thorns
Chamaerops humilis European fan palm FG
Plumeria obtusa Singapore plumeria 30-35' m-f FG M E
Plumeria rubra f. rubra White plumeria 25-35' m FG G E
Plumeria rubra f. acutifolia Red plumeria 20-25' m-f FG M E
Bauhinia binata Alibangbang 25-35' s-m M G
Brexia madagascariensis Brexia 20-30' s M G
Cerbera manghas Cerbera 20-25' m M M
Chrysalidocarpus lutescens Areca palm 20-30' m M
Erythrina crista-galli Common coral 12-20' m M G
Feijoa sellowiana Pineapple guava 15-18' s M M Attractive bark
Ficus carica Fig tree 10-30' m-f M M G
Guiacum officianale Lignum-vitae 25-35' s M G
Jatropha integerrima Peregrina 15-20' m M M
Morinda citrifolia Noni 10-20' m M M Remove fruits
Phoenix silvestris Wild date palm 30-50' s M
Psidium guajava Common guava 20-30' m-f M G Fruits can litter; attractive bark
Psidium littorale Yellow strawberry guava 20-30' m M G Fruits can litter; attractive bark
Senna surattensis Kolomona 10-25' f M M
Stenocarpus sinuatus Firewheel tree 25-30' s-m M M G
Strelizia nicholai Bird-of-paradise-tree 20-30' s-m M M
Thevetia peruviana Be-still tree 20-30' m-f M G E Takes drastic pruning; slightly poisonous
Trachycarpus fortunei Windmill palm 20' M
Veitchia merrillii Manila palm 15-20' m M
Yucca elephantipes Giant yucca 20-30' s M G

3. Shrubs that can be pruned into small trees

Botanical name Common name Height Growth
Salt Wind Heat Comments
Ilex vomitoria Youpon holly 20-25' s-m E E
Callistermon citrinus Weeping bottlebrush 20-30' s-m G G
Callistermon rigidus Stiff bottlebrush 15-20' s G G G
Calotropis gigantea Crown flower 12-15' m G G
Dracaena marginata Money tree 10-25' s-m G G
Duranta erecta Golden dewdrop 8-18' m-f G G
Euphorbia tirucalli Milkbush 20-30' G
Hibiscus tiliaceus Hawaiian hibiscus tree 9-30' f G G G
Myporium sandwicense Naio, False sandalwood to 30' f G G G
Nerium oleander Common oleander 20-30' f G G G Some may be salt-sensitive
Nototrichium sandwicense Kulul to 12' m G-M E
Callistemon viminalis Drooping bottlebrush 20-30' m-f M F
Canthium odoratum Alahee 10-20' s M G Native
Cycas circinalis Queen sago 6-12' vs M G
Hibiscus rosa-sinensis Chinese hibiscus 15-30' m-f M M G Some may be salt-sensitive
Hibiscus schizopetalus Coral hibiscus 6-12' f M M
Pittosporum tobira Pittosporum 10-25' s-m M Some may be salt-sensitive
Pittosporum udulatum Victorian box 15-40' mf, s M Alkaline soils OK, grows fast to 15', then slow
Podocarpus elatus Pine-tint podocarpus to 30' s M G
Podocarpus macrophyllus Japanese yew 25-50' s-m M Some may be salt-sensitive
Rhapis excelsa Bamboo palm 5-10' s-m M
Ligustrum japonicum Japanese privet 10-15' m-f M-G G Some may be salt-sensitive

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Eileen Herring, eherring@hawaii.edu
Hamilton Library, UH Manoa

Comparison of Container Placement Patterns for Maximizing Greenhouse Space Use.
E. Will, J.E. Faust, and B.B. Burgoa. 1999. HortTechnology 9(3): 432-435.
Efficient use of greenhouse space requires knowing how many plants will fit on a bench or floor area. Nurseries frequently use square spacing with each pot lined up with the pots in the adjacent rows because it is easy for the workers to handle. The usual way of calculating the number of containers that will fit on a bench using this type of spacing is to divide the total area of the bench (length x width) by the area of the container, calculated as if the container was square. This approach gives an incorrect answer since, in reality, it is not possible for the containers to occupy the entire surface; that is, you cannot fit partial containers at the ends of rows. These researchers developed a series of equations to calculate the number of containers that can be put into a specific area using three different arrangements: square, long-staggered, and short-staggered. In comparisons of the three patterns, staggered spacing frequently allowed up to 13% more containers to fit into a given area. This difference can affect overhead costs from $0.02 to $0.20 per container for a 10-week crop. A Microsoft Excel spreadsheet that assists with these calculations called the Bench Crop Calculator is available from the authors. They can be contacted at the Department of Ornamental Horticulture and Landscape Design, The University of Tennessee, Knoxville, TN 37901.

Effect of Fertilizer Concentration on Growth of Double Impatiens.
B.E. Whipker, S. Dasoju, M.S. Dosmann, and J.K. Iles. 1999. HortTechnology 9(3): 425-428.
Providing the necessary mineral elements in the appropriate concentration is important for optimal growth of ornamental plants. Excessive fertilization or insufficient leaching can result in slow growth, limited root development, and stunted plants. Under high fertilization rates, the authors observed that variegated forms of double impatiens (Impatiens wallerana) had rippled or cupped leaves while the leaves on green forms were undistorted. In the work reported in this paper, rooted cuttings of double impatiens cultivars 'Blackberry Ice' (variegated) and 'Purple Magic' (green) were potted in 4 inch pots with a planting mix of 2 parts soil, 5 parts sphagnum peat, and 3 parts perlite by volume. These plants were grown on flood benches and irrigated with Excel 15-5-15 Cal-Mag at rates of 50, 100, 200, or 300 ppm (mg per liter) of nitrogen. At the end of nine weeks, these researchers found that the 'Purple Magic' (green) cultivar grew best at the 100 ppm rate while the 'Blackberry Ice' (variegated) cultivar required a lower rate between 50 and 100 ppm. Since flood bench grown plants require 33% to 50% less fertilizer than hand watered plants, the authors suggest rates of 150 to 200 ppm of nitrogen for hand watered plants, using the lower end of the range for the 'Blackberry Ice' cultivar.

Resistance in Twenty-two Cultivars of Spathiphyllum to Cylindrocladium Root Rot.
D.J. Norman, R.J. Ehnny, and J.M.F. Yuen. 1999. HortTechnology 9(1): 68-69.
The most damaging disease during spathiphyllum production is root rot caused by Cylindrocladium spathiphylli. Two spathiphyllum species have shown resistance to Cylindrocladium root rot (CRR), but these species have little ornamental potential and do not hybridize with existing commercial cultivars. In this study, twenty-two popular commercial spathiphyllum cultivars were evaluated for resistance to four different isolates of Cylindrocladium spathiphylli. Two of the isolates were from Florida and two were from Hawaii. (The most sever symptoms in this research were those produced by the isolates from Hawaii.) None of the spathiphyllum cultivars tested were highly resistant to CRR. However, the cultivars 'Chris' and 'Textura' showed some resistance to all four isolates being tested. Results from this type of cultivar screening can encourage the selection of more resistant breeding lines and create a baseline for comparison of resistance in newly developed cultivars.

Using Isothiazolone Biocides to Control Microbial and Fungal Contaminants in Plant Tissue Cultures.
R.P. Niedz. 1998. HortTechnology 9(4): 598-601.
Microbial and fungal contamination is one of the most persistent problems in plant cell and tissue culture. Antibiotics or fungicides are generally used to control persistent or externally introduced contaminants. These are not always effective, can alter plant growth, are costly, and can contribute to the development of resistant strains of microorganisms. This research tests a commercially available plant preservative mixture (PPM) for use in controlling growth of contaminating organisms in plant tissue culture media. PPM is produced by Plant Cell Technology in Washington, D.C. and contains a mixture of two isothiazolones. Isothiozolones are a class of broad-spectrum biocides used in a variety of industrial applications. The manufacturer states that the isothiazolones used in PPM are not phytotoxic at concentrations suitable for use in preventing microbial contamination of plant tissue cultures. The effects of PPM were tested on in vitro cultures of citrus seed, callus, protoplasts, and epicotyl explants. The only significant phytotoxicity observed in these experiments was to freshly isolated protoplasts. These were initially very sensitive to PPM, but this sensitivity disappeared after 5 days. The researcher concludes that PPM appears most effective in inhibiting the growth of air- and water-borne bacteria and fungi at low inoculum densities. Since it can be autoclaved with the medium without losing its effectiveness, it is suitable as a preservative agent in culture media to control low-level contamination.

Thermoperiodicity in Shoot Elongation of Purple Nutsedge.
W.H. Sun and R.K. Nishimoto. 1999. Journal of the American Society for Horticultural Science 124(2):140-144.
Tubers of purple nutsedge (Cyperus rotundus) sprout in response to temperature. This research shows that an early stage of sprouting, bud elongation, is specifically a response to multiple alternating high and low temperatures. The best temperature for purple nutsedge shoot elongation is 958 F (358 C). In these experiments, shoot elongation was greatest when temperatures varied than at any constant temperature. This ability to respond to daily temperature changes is an important adaptation for purple nutsedge. When soil is shaded by other plants, the temperature doesn't fluctuate very much and few nutsedge will sprout. Open conditions or sparse plant canopy increases the daily variation in the soil temperature and results in tubers sprouting in these more favorable conditions. Soil solarization increases the daily fluctuation in soil temperatures and research in Hawaii has shown that about 98% of the tubers will sprout after solarization. Solarization to stimulate growth of the majority of dormant nutsedge sprouts followed by application of an effective herbicide may be a useful control method for this difficult weed.

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Visit the CTAHR web site, www2.ctahr.hawaii.edu and go to the publications section to find the latest on new CTAHR publications.

New for-sale publications
Order blanks for CTAHR's for-sale publications can be downloaded from web site at:

Growing Coffee in Hawaii, 40 pp.
(revises and updates the classic 1950s brochures by Y. Baron Goto and Eddie Fukunaga)

HNRIS--Hawaii Natural Resource Information System
(includes CD-ROM; download the instruction manual from the free publications page for an overview of this PC-based geographic information system)

New free publications CTAHR's free publications can be downloaded from the college web site at www2.ctahr.hawaii.edu/oc/forsale. Printed copies can be requested by calling 808-956-7046 or sending e-mail to ctahrpub@hawaii.edu.

Financial Connections
Buying your first new car, FC-49
Saving the Roth way hits the spot, FC-50
Rental car insurance: who needs it? FC-51

Foods and Nutrition
Be safe: a home guide to help keep food safe, FN-5

Home Garden Vegetable
Lettuce for the home garden, HGV-2

Turf Management
Dogs and lawns, TM-11

Economic Issues
Agriculture's contribution to Hawaii's economy, EI-2

New Plants for Hawaii
'Mauna Loa' anthurium, NPH-A-2

Ornamentals and Flowers
Liriope, the "other" mondo grass, OF-29

Resource Management
Seed technology for forestry in Hawaii, RM-4

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This newsletter is produced in the Department of Horticulture, a unit of the College of Tropical Agriculture and Human Resources (CTAHR), University of Hawaii at Manoa, as a participant in the Cooperative Extension Service of the U.S. Department of Agriculture. CTAHR is Hawaii's Land Grant institution established in 1907 from which the University of Hawaii developed. For information on CES horticulture programs or to receive future issues of this newsletter, please contact:

Jay Deputy or Kenneth Leonhardt
Department of Tropical Plant and Soil Sciences, University of Hawaii
3190 Maile Way, St. John 102
Honolulu, HI 96822-2279

(e-mail Jay Deputy, Kenneth Leonhardt)

Mention of a trademark, company, or proprietary name does not constitute an endorsement, guarantee, or warranty by the University of Hawaii Cooperative Extension Service or its employees and does not imply recommendation to the exclusion of other suitable products or companies.

Caution: Pesticide use is governed by state and federal regulations. Read the pesticide label to ensure that the intended use is included on it, and follow label directions.

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Thank You. We hope you enjoyed this issue of Landscape, Floriculture, and Ornamentals News.

Kenneth Leonhardt, leonhard@hawaii.edu
Extension Specialist in Horticulture

James C. Deputy, deputy@hawaii.edu
Education Specialist

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