Pruning

Careful pruning of coffee trees is one of the most important cultural practices. Improper pruning can reduce yield and subject trees to biennial bearing, often resulting in dieback, when leaves, fruit, laterals, and sometimes verticals die before harvest due to exhaustion of nutrients, particularly N, and depletion of carbohydrates in the tree due to overproduction of fruit. The farmer must prune correctly for efficient annual production and healthy trees.

The principle objectives of pruning are:

  1. to control biennial bearing through control of flowering and fruit setting;

  2. to regulate the age of the bearing portion of the tree by training and shaping it into a predetermined form or pattern, and

  3. thereafter to maintain the tree in a young and productive condition.


Three pruning systems are currently practiced in Hawaii:

  1. "Kona style",

  2. the Beaumont-Fukunaga (BF) method, which is the standard in much of Latin America and is becoming popular in Kona, and

  3. the mechanically hedged and topped system (HAT) used on large coffee farms on Molokai, Kauai, and Maui.



Figure 54. Before and after rejuvenation pruning. Tree on left is over 12 tall, back right hedged to 5' by 5' , tree in front was stumped to 1.5'.


"Kona style" pruning

"Kona style" pruning, the most popular pruning style in Kona (Fig. 2), is a multiple-age vertical system. If done properly, it accomplishes the objectives of pruning mentioned above in addition to admitting light to various parts of the tree, encouraging the type of growth and fruiting that will permit easiest hand harvest with the least reduction of yield, encouraging the production of uniform, high-grade coffee cherry, and facilitating the effective control of insects. On the negative side, annual hand pruning is required, and a good understanding of the system is essential to select the appropriate verticals for removal. This system cannot be mechanized except to use chain saws and power loppers instead of hand tools.

The number of verticals to be maintained on each tree depends on several factors, including the inclination of the farmer, soil fertility, planting distance, sunlight, rainfall, and other factors affecting the growth and fruiting habits of the trees. There may be as many as 10 or as few as four verticals on each stump, as determined by these conditions.

Two variations of the "Kona style" system described below are known as the "four-vertical 1-2-3-4 type" and the "six-vertical 1-2-3-4 type."


Training for the "Kona style" system

Two methods of transplanting can be used. In the first method the upper half or third of the seedling is removed when transplanting into the orchard. A second method is to transplant the seedling at an angle of 10-30 degrees. Both methods force the production of new verticals.

First year: During the first year the objective of training consists of selecting and developing two to four strong and vigorous verticals and removing all others. The number of verticals allowed to grow depends on the vigor of the plant.

Second and third year: Remove any suckers (new verticals) developing on the trunk or on the selected verticals.

Fourth year: The tallest vertical, or the one which appears to be the oldest, should be removed at the trunk during the winter or spring. Allow one or two new verticals to develop during the year.

Fifth year: Remove one of the remaining old verticals to make room for one or two new verticals.

Sixth year: Remove one or two of the remaining old verticals and allow new verticals to develop. This will just about start a new cycle of pruning.


No vertical should be allowed to remain on the stump longer than five years under the multiple-age vertical system, with four years generally considered the best time for removal.


Four-vertical 1-2-3-4 "Kona style"

This is the simplest variation of a multiple-age vertical system (Fig. 2). The trunk of the tree may be of any age (some in Kona are 100 years old). Four verticals only are allowed on the stump at one time. The system is maintained by cutting the oldest vertical each year about 3 inches from the trunk and allowing a new one to replace it, thus completely renewing the verticals every four years. Any suckers that grow on the trunk or selected verticals are removed as well.

This system enables the farmer to keep approximately the same bearing surface on the tree year after year, and it will produce about the same size crop annually. The trees are relatively certain not to suffer from the problem of biennial bearing and possible dieback.

Vertical 1, which replaced a four-year-old vertical after the last crop was harvested in the fall of 1998, will be left on the stump until 2002 when, after harvest, it will itself be replaced. Vertical 2, which replaced a four-year-old vertical in 1997, would be two years old in 1999. It will be replaced at the age of four years in 2001. Vertical 3, which replaced an older vertical in 1996 and would be three years old in 1999, will be replaced after harvest in 2000. Vertical 4 is four years old this year, 1999, and will be replaced after harvest of the current 1999 crop.


Six-vertical 1-2-3-4 "Kona style"

Six verticals are maintained in this system. These are replaced on a systematic basis in the manner of those in the 4-vertical system, however, two verticals are replaced every other year, and one in each alternate year. The system is recommended for trees planted at distances of 9 x 9 ft or wider in sunny areas that have adequate rainfall and high fertilization.


Time of pruning

Pruning is most profitably and effectively done from just after harvesting through the semidormant period, January through March. This holds for all of Hawaii's coffee areas, as the tree is semidormant due the cooler temperature and shorter daylength of our winter months.

When the harvesting season continues throughout the year, as in upper elevation (cooler), rainy areas where seasonal changes do not affect regular seasonal characteristics in flowering and fruiting, it may be necessary to prune at various times. Under these conditions, old verticals may be removed by sawing through them partially and bending them over without completely severing them. The sawing should be done just before a given round of harvesting. This will allow the cherries on the partially severed verticals to mature while new verticals develop just below the point of sawing. After the cherries on the cut verticals have matured and been harvested, the verticals may be completely severed and removed from the tree.


Removal of suckers

It is important to remove unwanted young verticals, called "suckers," which the farmer does not wish to develop into bearing verticals. This can be done when the suckers are 3-6 inches in length, at which time they can easily be pulled off. If smaller, they can simply be rubbed off with the palm of the hand. In Kona, these unwanted branches grow most prolifically during the rainy months of April to August. The usual practice is to remove them every other month during this period. This is a must for the "Kona style" pruning, but it is usually not necessary in hand-pruned Beaumont-Fukunaga systems after the first year. Removal by hand is not feasible in mechanical pruning systems. Suckers low on the trunk are killed by postemergent, contact herbicide applications (e.g., Gramoxone®) when controlling volunteer coffee and weed seedlings.

Relationship of rainfall, fertilization, and pruning practices The following discussion of factors affecting yield applies to the "Kona style" system (Goto and Fukunaga 1956); the application of this information to mechanized pruning systems is still being studied.

Rainfall, irrigation, fertilizer application, and pruning practices are all closely related to coffee yield. A major goal is to have regular annual bearing, avoid overproduction and the resulting biennial bearing pattern, and discourage conditions that result in overbearing dieback. The amount of fertilizer and the degree of pruning to be done are determined to a large extent on the basis of rainfall during the preceding and current crop years, as well as last year's yield and the current crop load.

If the previous crop was small and rainfall was heavy, in the current year the tree can be expected to have a lot of bearing wood. To prevent overproduction, both the amount of fertilizer applied and pruning should be heavy. By fertilizing heavily and pruning off an adequate amount of bearing wood, the tree is provided a food supply to develop the current crop and a reserve supply to support a moderate yield in the following year. If, on the other hand, the tree was allowed to fully utilize all its bearing wood during the current season, there is danger of overproduction, severe dieback, and an unprofitably light crop the following season. Dieback will reduce the crop for several years and in severe cases may even kill the trees.

If the orchard has suffered from low rainfall during the current year, resulting in light growth of bearing wood and exhaustion of stored plant food, pruning for the following year should be light. The bearing wood that developed during the preceding year is light, and therefore the crop will be light.

If rainfall is normal, the trees tend to develop new wood excessively. The amount of fertilizer should be reduced accordingly, thus limiting vegetative growth, preventing overproduction in the following year, and providing against the occurrence of overbearing dieback.

The avoidance of overbearing dieback-resulting in biennial production, lower production, and even tree death-is the chief aim of pruning. The farmer must carefully appraise the size of the crop and the amount of vegetative growth during any given year in order to determine the degree of pruning and amount of fertilizer to be applied the following year. The schedule shown below is a guide for regulating fertilizer and pruning programs to attain consistently moderate yields, which are in fact the best annual efficient crop yield.

Each coffee tree in an orchard has individual characteristics that must be taken into consideration. This diversity demands flexibility in the application of the pruning method. Very rarely is this style of pruning applied uniformly to every tree in an orchard. Each tree is managed according to its characteristics. The good farmer knows each of his trees well.


Beaumont-Fukunaga (BF), a multiple-same-age vertical pruning system

This system was developed at the Kona Research Station by John Beaumont and Edward T. Fukunaga in the 1940s and 50s. Its initial popularity in Kona diminished, but it became widely used in Central and South America. In the 1990s, the Beaumont-Fukunaga system is being tried again in Kona. Instead of renewing one or two verticals in each successive year as in the "Kona style," all the verticals on the tree are renewed in the same year every 3-5 years (Fukunaga 1959).

The BF pruning system has three variations: the four-year/four-row 1-3-2-4 (Fig. 3), the three-year/three-row 1-2-3, and the five-year/five-row 1-3-5-2-4. All verticals on the trunk are removed at one time; in other words, the tree is cut (stumped) 18-24 inches above the ground, usually with a chain saw. This height is for ease of desuckering and harvesting by hand. If the trees are mechanically harvested, we currently recommend the cut should be above the height of the catching pans to reduce dropped fruit. The number of verticals allowed to develop on each trunk may vary from three to six, depending upon the spacing of the trees in the row (usually 21/2-6 ft). In Kona, where the distance between rows is 7-10 ft, this row-pruning sequence is 1-3-2-4 and is repeated across the orchard. Because the rows are usually spaced less than 10 ft apart, pruning is done in alternate rows, which results in more efficient interception of sunlight. Shading is reduced because with the 1-3-2-4 pattern the rows with the tallest verticals (the 3- and 4-year-old verticals) are not side by side.

Usually, the trees produce many suckers in response to stumping. The number of suckers allowed to become verticals must be limited to three to six, depending on the tree spacing. If this is not done and there are too many verticals, the first harvest after pruning will be small because there will be few flowers per node due to shading within the tree. Yields in subsequent seasons in the remaining cycle of those trees may also be smaller.

When the suckers are about 12 inches tall, reduce their number to about 11/2-2 times the final number desired on each trunk. This can be by hand (gloves are recommended) or with a hand pruning tool. Remove suckers that are weak, deformed, or low on the trunk. The suckers selected should be spaced evenly around the trunk to reduce shading.

When these verticals are 18-24 inches tall, which is usually by May-June, remove any new suckers and thin the verticals to the desired number-plus one extra-per trunk. The extra one is to replace any lost due wind or other damage. This is important in windy areas or if the final number verticals per trunk is low (three or four). This second round of desuckering and thinning should be done with hand pruners to avoid ripping the bark. If this operation is delayed (for example, until November or December), shading may have caused new laterals to die or a low number of flower buds to form.

Remove the extra vertical left as a safeguard against wind in August-October. Remove any new suckers. After this stage, there should be sufficient shade to prevent or retard the growth of new suckers.

In the 3-year cycle system, the pruning sequence is 1-2-3. In the 5-year cycle, the sequence is 1-3-5-2-4. Row 1 is stumped in the first year, row 3 is stumped in the second year, row 5 is stumped in the third year, row 2 is stumped in the fourth year, and row 4 is stumped in the fifth year. The 4-year cycle is recommended for higher elevations, and the 3-year cycle is most suitable for lower elevations. Orchards planted to dwarf cultivars such 'Red Caturra' or red or yellow 'Catuai', or located in cloudy areas, may perform better with the 5-year cycle.


BF system for mechanized farms

The Beaumont-Fukunaga system for mechanically pruned and harvested orchards is modified compared to orchards pruned and harvested by hand. The trees can be stumped with rotary saws on a rotating arm mounted on a tractor (see Sources, p. 2). Or, a mechanical harvester can be rebuilt with fixed rotary blades. Several passes are generally required, plus passes with a tractor-mounted chipper to mulch the prunings in place.

Suckers can be controlled by "burning" them with a spray of a highly concentrated foliar nitrogen fertilizer, such as urea ammonium nitrate (UAN, 32-0-0) or a 25-50 percent urea solution. Another method is to use a postemergence, contact herbicide such as Gramoxone® during the standard weed control program. Do not use a systemic herbicide, such as Roundup®, for sucker control-it will seriously damage or even kill the tree.

The objective in pruning with contact herbicide is to spray weeds (including volunteer coffee seedlings) in the row as well as suckers on the trunk. On one side of the row, direct the spray from the ground to close to the top of the trunk; on the other side, spray lower, from 6 inches below the top of the trunk to the ground. This results in an area where the suckers are allowed to develop, and elsewhere the suckers are killed. Several sprays will be necessary, and they should be started when the suckers are 3-6 inches tall, particularly when using the concentrated fertilizer solution, which will not kill larger suckers. Do not spray in windy conditions, unless using a shielded sprayer with fan or herbicide nozzles. Practice on a row to see how it works before spraying all the trees.

Pruning should be done by block instead of by row. An orchard is divided into three blocks for a 3-year cycle, four blocks for a 4-year cycle, and five blocks for a 5-year cycle. The advantage of blocks over rows is that irrigation, fertilizer application, weed control, harvesting, and other cultural practices can be managed more efficiently in blocks of rows rather than in alternating rows within a block. Also, unnecessary travel in the alleys between rows is avoided.


Advantages of the BF system

Some of the advantages of the BF system are:

Mechanically hedged and topped system (HAT)

Tall and dwarf varieties can be hedge-pruned. Hedging can be done for hand-harvested coffee, but the long-term yield and ease of harvesting may be less than with the "Kona style" pruning, although in a three-year comparison it was superior (Bittenbender 1996). For mechanically harvested orchards, or when sufficient labor is either lacking or too expensive, the HAT system performs well (Fig. 4).

A sickle-bar type hedge pruner that is hand-held or mounted on a tractor can be used. Special rotary saw blades mounted on a frame or on a rotating arm can be used (e.g., the TOL pruner; see Sources, p. 2). The appearance of the hedge after pruning with rotary blades is not as "tidy" with a sickle bar, as some branches will be left uncut. Saws are more robust than sickle bars, as leaning verticals can jam a 2-inch sickle bar. The tree is cut horizontally (topped flat) at 5 ft in height. This can be done with the same equipment, unless the verticals are too thick for a sickle bar. Pruning can be done after harvest, up to May. Which year to prune in is based on the tree size and expected yield; if too tall or wide to easily harvest and the crop will be small, then prune.

The hedging will stimulate the regrowth of sub-laterals. The topping will bring light into the center of the tree, resulting in the production of new verticals on remaining old verticals but particularly at the top near the cut. New primary laterals will be produced on these new verticals. In summer, the tree should be topped again near the first topping to further encourage production of new sublaterals. Yield in this year will be small in most cases.

In years 2, 3, and 4, the trees are topped after flowering just below the highest fruit set, or limited to 12-18 inches of new top growth. It may also be advantageous to lightly hedge (tip) the sides to further encourage the production of sublaterals or if the crop load is very heavy, particularly in year 2.

When the trees need pruning again, probably in three to fours years, hedge again at 5 x 5 ft. Trees pruned with this system have produced good yields for 10 years (three cycles). The BF (stumping) system is a more radical approach to tree rejuvenation and may be necessary after several cycles. Research to further refine mechanical pruning is in progress.


Advantages of the HAT system