Coffee has been grown commercially for more than 170 years in Kona, despite periods of adverse economic conditions. While coffee was grown earlier in other locations in Hawaii, it was not continuously cultivated, and coffee grown in areas other than Kona never attained great importance until the 1990s.
Figure 2. Location of principal coffee production areas in Hawaii.
Many factors have contributed to the development of the Kona coffee industry. A historical one was that large-scale agriculture, such as sugarcane or pineapple plantations and ranching, was more profitable elsewhere in the islands. But the principal factor is that the climate of the Kona region is ideal for coffee. Its spring and summer rainfall pattern is more favorable for coffee growth than the winter rainfall normally received by much of the state. When rainfall coincides with warm temperatures, the conditions are optimum for plant growth and fruit development in coffee and many other fruit crops. Furthermore, Kona's cool, dry winter is conducive to maturing the coffee fruits ("cherries") and forming flower buds for the next crop.
In locations in Hawaii other than Kona where coffee has been grown in the past, experience to guide the prospective grower is either scant or forgotten. Accordingly, the prospective coffee grower outside Kona should proceed with care and caution.
Temperature is a key factor in coffee production, and the strongest influences on temperature are latitude and elevation. Coffee is grown around the world at latitudes from 24°N to 25°S and elevations ranging from sea level to as high as 7000 ft. In general, high-elevation coffee regions are found in countries at or near the equator, such as Kenya, the New Guinea highlands, and Colombia, while low-elevation coffee regions, such as Hawaii and Sao Paulo, Brazil, are usually at subtropical latitudes (22-25°). At any given latitude, coffee is often grown over a wide range of elevations. In Hawaii, it seems that most elevations between sea level and 2500 ft should be suitable for coffee, provided that rainfall and soil factors are favorable.
Coffee tolerates wide annual variations in temperature. In parts of Brazil's Sao Paulo and Parana states, coffee trees are injured by frost almost every year, and freezes occasionally kill them. In the summer, however, coffee in these regions experiences very hot and humid conditions. A more moderate climate for coffee is found in one of the most important coffee-growing districts of Colombia, Chinchina, where the mean minimum temperature is 60°F, the mean maximum is about 80°F, and the mean monthly temperatures seldom vary more than 2-3°F throughout the year.
High temperatures (> 90°F) before and during flowering may result in abnormal coffee flowering and poor fruit set. In Kona (as in Brazil), the low winter temperature and rainfall seem conducive to regular annual flowering. In Colombia, on the other hand, where temperatures are neither too high nor too low and extremes are not encountered, dry periods seem to be of greater significance in affecting flowering.
Cloudless, dry, high-temperature areas such as Kekaha on Kauai or Waianae on Oahu are not favorable to coffee. However, successful coffee production is found in low-rainfall areas at elevations as low as 200 ft, such as Eleele on Kauai and Kapalua on Maui. In windward areas of Hawaii, Maui, Kauai, and Oahu, where rainfall is abundant and temperatures are relatively constant, coffee flowering and harvesting seasons may be more irregular and unpredictable than in Kona, with its more pronounced seasonal conditions. In such windward areas, special crop management practices may be necessary for coffee production to be commercially feasible.
Shading with one or more layers of trees is practiced in some tropical coffee-growing areas, but in the subtropics of Hawaii and Brazil it has been found to be unnecessary. If an area is too warm for coffee, shade might help. In the countries where shade is traditionally used, fertilizers are often in short supply, and the soil fertility is often inadequate to support a large crop. Under these conditions, restricting light with shade reduces the number of flowers per node, limiting production and helping prevent dieback due to overbearing. With adequate fertilizer and good management in Hawaii, however, high yields can be supported under full sun without dieback. Thus from the standpoint of coffee management, there is little use for shade in Hawaii. From the environmentalists' point of view, there is some interest in having shade trees in Central American coffee orchards to support bird populations--particularly migratory birds from the U.S. mainland.
Coffee should not be planted in sites exposed to tradewinds or severe "kona" storms without a well established windbreak. Wind bends young coffee trees, causing more vertical stems than desired to be produced, and this may reduce yield. Severe winds cause "cupping," tearing, and removal of leaves-and sometimes removal of ripe cherries.
Temporary windbreaks are essential for newly transplanted trees in windy areas; a single row of densely sown Sudax, a sterile hybrid of sorghum and sudan grass, in the middle of the alley between coffee rows, is recommended (see Sources, p. 2).
Figure 3. Coffee transplanted by hand through plastic mulch with drip irrigation under mulch. Sudax was 3 months old, its serves as a windbreak for transplants.
Sudax should be planted at least six weeks before the coffee is transplanted and sown at a minimum rate of 2 lb/acre (nine seeds per foot of row, assuming the coffee rows are 12 ft apart). If access by equipment during this establishment period is essential, plant the Sudax closer to the windward side of the coffee. Birds can be a problem during germination. The windbreak should receive fertilizer, and irrigation may be necessary. It should be 3-4 ft tall when the coffee is transplanted. After 18 months, when the coffee is 4-5 ft tall, the Sudax can be killed by plowing or spraying a grass herbicide (this method was described by Osgood and Chang 1994; see References, p. 40).
Coffee hedgerows can serve to break wind velocity for the orchard, although severe wind-pruning will likely occur in the rows exposed to wind intensity. A system of taller, permanent windbreak plants is preferred. A windbreak protects a downwind distance as much as 10 times its height. Some farms combine two types of tree windbreak. When the coffee trees are young, protection is provided by the tall, narrow, fast growing 'Tropic Coral' wiliwili (Erythrina variegata) planted 3-4 ft apart in rows 100-150 ft apart. As the orchard matures, it is protected by taller trees such as Norfolk Island pine (Araucaria excelsa) or a non-spreading type of ironwood (Casurina cunningham-iana) planted 6-8 ft apart in rows 600-800 ft apart.
Figure 4. These windbreaks should be planted before the coffee. The wiliwili is in the front, and repeated again before the tall Norfolk Islands pine.
Some coffee-producing areas have annual rainfall of only 30 inches, while other areas receiving over 100 inches of rain also have good production. Optimum annual rainfall for coffee in Hawaii is considered to be 60-85 inches. However, the most important factor is the rainfall distribution pattern as it relates to the various phases in the coffee growth cycle: vegetative growth, flowering, maturing of coffee cherries, ripening, and harvesting. Excessive moisture stimulates vegetative growth at the expense of fruiting. If rainfall is uniformly distributed, flowering and fruiting will occur almost throughout the year. A short dry period, ideally occurring during the coldest part of the year, helps to synchronize the cropping cycle, inducing flower bud growth by satisfying coffee's requirement for dormancy prior to flowering.
Irrigation is essential in Hawaii's recently planted dry coffee-growing areas, such as Kaanapali on Maui, Eleele on Kauai, Kualapuu on Molokai, and Waialua on Oahu. These areas are characterized by dry summers and wet winters, although the winters are not as wet as a Kona summer. New orchards have also been planted in high-rainfall areas, along the Hamakua coast and in Puna on Hawaii and in Hana on Maui, where rainfall can exceed the optimum. So far, the coffee harvest in these areas appears to coincide with the August-December harvest season that is normal elsewhere in Hawaii.
Coffee grows best on deep, porous, well drained soils, especially those of volcanic origin. Soils with excessively leached topsoil, impervious subsoil layers, or solid rock close to the surface will not support healthy coffee trees. Coffee will not do well and can die on heavy soils if drainage is a problem or if the soil is kept continually waterlogged below the surface.
Figure 5. Trees on the right, have poor growth, laterals died, due to poor drainage in a high rainfall area, probably rock close to the surface resulting in standing water on the surface or just beneath.
Some soils in Kona and elsewhere in Hawaii are of recent origin and appear to be almost pure lava. Coffee does surprisingly well in such soils where the rainfall is abundant and well distributed (or irrigation is available) and fertilizer is applied in proper amounts. Greater and more rapid leaching of fertilizers is expected in these locations, so applications must be lighter and more frequent.
During drought on rainfed a'a lava land, particularly when the trees are bearing fruit, it may be impossible to maintain healthy trees. The trees will suffer leaf dieback, lose fruit, and possibly die. This damage in dry years will be less likely to occur if the trees are widely spaced and kept in optimum growing condition by light and frequent fertilizer applications, pruning to maintain only a few verticals, mulching, and controlling weeds.
The Kona coffee belt
During the past 100 years, experience has shown that coffee production is ideal in a narrow zone in Kona approximately 20 miles long and 2 miles wide known as the "coffee belt." This "lower humid zone" runs almost parallel to the coast line. It begins in the north at Palani Junction and extends south to Puuhonua Road, and it lies between approximately 700 ft and 2000 ft elevation.
Kona Coffee Country
Figure 6. Map showing the Kona coffee belt.
The temperature in this area is ideal. At CTAHR's Kona Research Station in Kainaliu (1460-1670 ft elevation) in the heart of the coffee belt, the annual average temperature is 69°F, the average minimum is 60°F, and the average maximum is 78°F. The seasonal drop in temperature occurs simultaneously with drought, causing the coffee trees to slow their growth and develop flower buds. The temperature for December, January, and February at the Kona Research Station averages 67°F (57°F minimum, 77°F maximum).
Another characteristic of the coffee belt is an ideal amount and distribution of rainfall, such that coffee in Kona usually has not been irrigated. The annual rainfall averaged 68 inches historically, but since the Kilauea volcano began erupting in 1983, it has been drier, averaging 49 inches. The seasonal rainfall distribution provides a short, dry period during the winter months that forces the coffee trees into a state of semi-dormancy, which promotes a subsequent flowering. This dry period is followed by gradually increasing rainfall as the crop continues to maturity. As the harvest season approaches, rainfall decreases, and the winter dry period begins the fruiting cycle again.
Average Monthly Rainfall
Figure 7. Average monthly rainfall, before and after the 1983 Kilauea volcano eruption, at the Kona Research Station in the Kona coffee belt, compared with Eleele, Kauai, a major new coffee site.
During the low-rainfall period of December-February, the last of the crop is harvested and the annual pruning is done. At the lower elevations of the coffee belt, coffee trees appear to be on the verge of dying from lack of moisture. But a week or two after the first soaking rain, usually in late February or March, buds that have been forming during the dry, cool period will bloom. Three to four blossoming flushes take place in March-April, each following a heavy shower. As rainfall is intermittent and not too heavy during these months, blossoming usually takes place on dry days, which, when followed by several additional dry days, ensures good fruit set. CTAHR research has demonstrated that at a dry site on Oahu, coffee trees at the right stage of development can be forced to flower by applying drip irrigation following an irrigation-free "drought."
After mid-April in the coffee belt, rainfall increases rapidly. High humidity and temperature promote rapid development of the current crop and the accompanying vegetative growth that provides the foundation for the next year's crop. Around mid-September rainfall decreases, facilitating harvest of the ripe cherries and slowing vegetative growth until semi-dormancy is forced by the cool, dry winter months.
Evaluating areas for potential coffee production
Selection of a suitable site for coffee planting on Kauai, Oahu, Molokai, or Maui, or in areas of the island of Hawaii other than Kona, should be made after careful study of the particular location. The key questions to ask are:
Maps showing the suitability of lands in Hawaii for coffee were generated by the CTAHR Hawaii Natural Resources Information System (HNRIS) using a series of statements about the crop's environmental requirements. The particular environmental aspects were ranked according to how difficult the condition is to correct. For example, it is hard to change the temperature, but soil moisture can be modified by irrigation. The computer mapping program used the following statements, listed in order from the most difficult to correct to the least difficult: