When hand-harvesting, only ripe coffee should be picked. Immature, overripe, and raisin (dried-on-the-tree) cherries are of inferior quality. Overripe cherries are soft and brown, and when they are squeezed, the individual seeds can be felt inside the fruit because the pulp and mucilage is gone. The "black bean defect" results from a cherry that rotted because it was repeatedly dried and rewet while on the tree. This is something that is more likely to happen in Kona or wet areas than in dryer areas.
In the lower part of the Kona coffee belt, coffee ripens from late August to December. The period from late September to early November is the busiest. By contrast, in the extreme upper (cooler), wet and cloudy section of Kona, the harvesting period can stretch throughout the year. The new coffee areas on Kauai, Molokai, Maui, and Oahu ripen from August to January. Any area being considered for coffee planting should have climatic conditions (a definite dry period) that will permit seasonal harvesting, rather than a long 8-10-month harvesting period, which requires labor throughout the year and costs proportionately more to manage. A long harvest period is the least efficient use of harvest labor, but it can be a useful strategy if the orchard is small and low-paid labor (family) is available in regular, short periods.
When the cherry has matured and is ready for picking, it usually turns from green to slightly red and then to glossy red when fully ripe. However, fruits of yellow-fruited varieties such as 'Yellow Caturra' or 'Yellow Catuai' remain yellow and do not turn red when fully ripe or even overripe. Another test for maturity for harvesting is if the seeds (the parchment coffee with bean inside) can be squeezed out by hand. If the fruit is hard and the seed cannot be squeezed out, the fruit is too immature to pulp. Under conditions of overbearing dieback, the fruit may turn from green to reddish brown. These fruits are usually smaller than normal and probably contain immature, low-quality beans; these fruits generally float and are removed during processing.
Coffee fruit on a tree does not mature all at once-several stages of cherry development will be found on a tree. Therefore, coffee harvesting practices differ in various parts of the world. Cherries are sometimes picked individually when ripe, as is done in Kona. Elsewhere, fruits of all stages of development are stripped at one time. Another strategy is that all cherries are allowed to become raisins and are stripped from the tree or gathered from the ground after they have fallen or been shaken down. In the machine-harvested areas of Hawaii, cherries of all stages, from green cherry to raisin, are harvested in single or multiple-pass harvests. Mechanical harvesters remove immature, ripe, and raisin cherries. These three products must be separated to ensure a highly uniform, quality product at roasting. Raisins are floated away, while the mature cherries sink in water. Immature or green cherries are separated from the ripe ones by a device called a classifier. Thus harvested cherries can be separated into three different parchment coffee products of differing quality.
In Kona, picking in four to eight rounds in any one season is common, with a month's interval between each picking. The number of rounds depends to a large extent on the elevation. In upper areas of Kona, the coffee is ripening almost the year around, while in lower areas, ripening occurs over a period of four months. Sometimes pickers are permitted to harvest three types of cherry: green-ripe, or mature green, which is mature coffee although not fully ripe and has a yellowish-green skin; hard-ripe, which is firm and red (or yellow); and soft-ripe, which is overripe, red to dark red, soft, and juicy. These three types, or what might be called ripeness stages, were noted as early as 1937 to have similar cupping qualities in tests conducted at the CTAHR Kona Research Station. However, a danger in picking the green-ripe cherries must be noted: at this stage, the beans are not sufficiently covered with mucilaginous coating to allow them to slide between pulping surfaces during the pulping process. Injury to the bean can thus occur, which will lower the quality of the pulped beans. This also applies to overripe and raisin fruits.
At the peak of the harvest season in Kona, experienced pickers gather between 200 and 400 pounds of coffee per day. To ensure quality, pickers must be instructed not to harvest immature cherry. There is a tendency for pickers to harvest immature cherry as the amount of coffee increases and the number of pickers available per harvest acre decreases.
The equipment needed for hand-harvesting coffee is simple and inexpensive: baskets for the individual picker, holding hooks for bringing branches into position for picking, and burlap bags for transporting cherries from the orchard to the processing area.
Coffee pickers in Hawaii in the past used baskets locally made from pandanus leaves; today, woven baskets are imported from Central America, and plastic baskets are also used. The capacity of these baskets is generally about 20-25 pounds of berries. The baskets may be suspended from the shoulder or fastened with a belt around the picker's waist.
The holding hooks are usually made of 3-4-foot long sticks of coffee or guava wood to which a cord is attached. The length of the cord is adjusted to the picker's height, in relation to the average height of the trees. The sticks are usually about 11/2 inches in diameter at the thickest end. A loop of wire tied onto the cord affords a place for the picker's foot, which can be inserted to hold the hooked branch in place while the picker removes coffee with both hands free. The hook-end may be simply the stump of a branch or a metal hook screwed into the stick. The picker must be instructed not to bend branches to the breaking point.
The coffee harvesters used in Hawaii in the late 1990s are manufactured by Korvan Inc. (see Sources, p. 2). Harvesters can be leased or purchased (cost is about $100,000). Harvesters from other manufacturers were tested in the late 1980s and early 1990s. The Korvan is a three-wheeled, self-propelled machine that straddles the row with finger-thick rods attached to 61/2-ft high spindles. Two multi-rowed spindles with fiberglass or nylon rods are carried on the harvester so that about half of each spindle's rods contact and enter the alley side of the coffee hedgerow. The rods vibrate, and the entire spindle turns as the harvester passes along the row. The vibrating rods knock off cherries directly and shake the laterals and verticals, which shakes off more cherries.
The cherries are collected at the base of the harvester on spring-loaded pans that form a "false floor" beneath the tree as the harvester moves over the tree. Cherries are diverted to conveyor belts that move them past fans, which blow off leaves and sticks, and deposit the cherries into a bin. The bin is emptied at the end of the row, and the cherries are taken for processing.
If all stages of cherry maturity-green, ripe, overripe, and raisin-are on the tree, the harvest will remove a certain percentage of each. These percentages vary with the cultivar and the tree's moisture status, as well as harvesting factors (type of harvester rod, harvester speed, and frequency of rod vibration; see Gautz 1999). In general, mechanically harvested cherry has percentages of the various maturity stages in the order raisin > overripe > red > green.
Ethephon®, which breaks down to ethylene, a natural plant hormone, is being registered for use on coffee. When sprayed on coffee trees at the appropriate time and concentration, it will increase the percentage of ripe cherries on the tree and reduce the force necessary to knock off ripe cherries. The Hawaii Agriculture Research Center is developing recommendations for using Ethephon. CTAHR has submitted the residue data required for registration with the EPA; final approval is expected in 2001.
A hand-held, air-powered, six-fingered harvest aid with fingers that open and close like a hand is being evaluated by some growers. The Spidy® knocks off cherries, and the fruit is collected from mats spread beneath the trees. All maturity stages of cherry are removed, and they must be separated to maintain quality.
In the second year after transplanting, a few hundred pounds per acre of cherry coffee will be produced in well managed orchards. When the price is low, farmers do not harvest this first crop, but at high prices, farmers may harvest and sell this small crop profitably.
In the third year, with optimum rainfall and good management of fertilizer and weeds, production may be in the neighborhood of 80 bags per acre (8000 pounds) of coffee cherry.
In the fourth year, 100 bags of cherry coffee can be produced under typical Kona conditions. The authors have observed similar yields on mechanized farms in dry areas, but we cannot predict such yields in wetter, cooler, cloudier areas elsewhere in Hawaii. The record at the CTAHR Kona Research Station is 196 bags (19,600 pounds) of coffee cherry per acre.