This is a brief guide to growing avocado trees in Hawaii

Chia, C.L.

Evans, D.O.

Chia, Chian Leng

Evans, Dale Ordway

ScholarSpace at University of Hawai'i at Manoa

HAWAII COOPERATIVE EXTENSION SERVICE Hawaii Institute of Tropical Agriculture and Human Resources University of Hawaii at Manoa COMMODITY FACT SHEET AV0-3(A) FRUIT AVOCADO C. L. Chia, Ext~nsion Specialist, Horticulture D. 0. Evans, Research Associate, Horticulture Family: Lauraceae Scientific Name: Persea americana Mill. Origin: American tropics Description Avocado is a much-branched evergreen tree 40 to 80 feet in height with elliptic leaves 3 to 10 inches long. Flowers are small, greenish, and perfect (having both male and female parts). Fruits are round, pear shaped (pyriform). or oblong, with skin varying from pliable to woody, smooth to rough and pebbly, and green, yellow, reddish purple, purple, or black in color. The flesh is greenish yellow to bright yellow when ripe, with a buttery consistency. Fruits have a single large seed making up 10 to 25 percent of the fruit weight. Varieties Avocado trees vary in size and adaptability to climate and soil type. They also vary in length of time from flowering to fruit maturity and, therefore, in season of maturity. Fruits of avocado varieties, or cultivars, vary widely in moisture and oil content, from less than 5 percent oil (with a watery texture) to more than 30 percent oil. Flesh texture should be smooth, but inferior varieties often have fibrous strings embedded in the flesh. Fruit weight ranges from about 1/4 lb to more than 3 lb. Three horticultural races are recognized: Guatemalan, West Indian, and Mexican. Many cultivars are hybrids between races and are not readily identifiable by race. Most cultivars grown in Hawaii are of the Guatemalan race, or are hybrids between the Guatemalan and West Indian races. Propagation Seedling plants fail to reproduce true to type, and grafting is necessary to maintain desired growth, bearing, and fruit characteristics. Grafted trees usually begin to bear fruit three to four years after transplanting. To avoid Phytophthora root rot contamination in the nursery when growing seedling rootstocks for grafting, ( 1) do not use seed from windfall fruits picked from the ground, (2) propagate seedling rootstocks in sterilized, disease-free media, and (3) do not allow containers to contact soil. Purchase only plants that have been grown with these standards of sanitation. Soil Types Avocado trees grow well on many soil types provided the soil is well drained. Planting sites should not have low areas where water stands after heavy rains. Poor soil drainage and soil pH less than 6.2 (acid soil reaction) favor development of Phytophthora root rot. Location Avocado trees are sensitive to sodium chloride and therefore are not suited to shoreline planting. Areas exposed to high winds should be avoided because branches are easily broken, and flowers and fruits may be damaged. Relative humidity of 50 percent or more is desirable during flowering and fruit set, so production in dry areas may be low. There is a great deal of variation among hybrid cultivars in adaptation to different elevations and temperatures. In Hawaii, Guatemalan and Mexican races and their hybrtds tolerate cool upland conditions and can be grown up to elevations of approximately 2000 to 2500 feet. Varieties of pure Mexican parentage, rarely grown in Hawaii, can be grown up to the frost line. The thin-skinned West Indian varieties, locally known as "summer pears," usually produce fruit of marginal quality when grown above 1000 feet. Cultural Practices Trees should be spaced 25 to 30 feet apart. Cultivation for weed control should be avoided by using herbicides; if practiced, cultivation should be as shallow as possible to avoid damage to the shallow avocado root system. Organic mulches are recommended for weed control and maintenance of good soil ~ondition. Pruning trees is usually unnecessafy except to shape young trees and remove dead branches. Heavily laden fruiting branches may be propped with poles. Important plant nutrients applied as f ertilizer1 to avocado are nitrogen (N) and calcium (Ca). Among the micronutrients, zinc (Zn) is. important to avocado and should be applied whenever deficiency is indicated. 2 If soil is strongly acidic, add calcium carbonate to raise pH to 6.2. If soil pH is adequate (pH 6.2 to 6.5). use calcium nitrate to provide calcium without increasing pH. Pollination Pollination is principally by bees. Two avocado flowering types, A and B, are distinguished by what time 'of day the flowers open. Each flower opens twice and is functionally female (pollen receptive) at first opening and functionally male (pollen shedding) at second opening. Type A opens first in the morning, closes about midday. and reopens in the afternoon of the following day. Type B opens first in the afternoon, closes in the evening, and reopens the following morning. Having trees of both types is important in orchards because production is improved by adequate cross-pollination (see Table 1). This is not as important in residential areas, however, where both tree types are usually present. Avocado trees flower during late winter and early spring in Hawaii. After fruit is set, some premature fruit drop is common and can be expected. Table l. Avocado varieties recommended for home garden plantings in Hawaii Flowering type Season of bearing A B Fall & winter San Miguel Semil-34 Winter & spring Greengold Hayes Spring & summer Ohata Case Kahaluu Nishikawa Sharwil Chang Murashige Source: HITAHR Brief 052, "Recommended Fruits and Nuts for the Home Garden." 1See General Home Garden Series No. 37, "Fertilizers for Fruit Trees in the Home Garden," and Circular No. 487,"How to Fertilize Trees and Shrubs." 25ee General Home Garden Series No. 24, "Foliar Application of Fertilizers." · Harvesting Fruits are picked when mature but still hard and then allowed to ripen. Mature fruits are full sized, may change color slightly or lose glossiness, and have brown seed coats. Determining maturity may be difficult and usually requires experience. Fruit should be harvested from the tree with pruning shears or special clippers and never pulled from the branch. The pedicel (fruit stem) should remain attached to the fruit. When the stem is pulled out. the fruit often spoils. Fruits are easily bruised, and windfall fruits are not marketable. Postharvest Fruit ripens only after falling or being picked. Ripeness is indicated by softening of the fruit. Fruit picked too early tends to shrivel and may fail to ripen. Determining the ripeness of thick-skinned varieties by feeling for softness may be difficult and requires some experience. Sometimes the pedicel is removed and a toothpick inserted to test fruit softness. but this method may permit entry of disease organisms. Fruit of some cultivars may be refrigerated without damage for several days after ripening. Diseases of Avocado Dodder ( Cuscuta sandwichiana) Avocado root rot (Phytophthora cinnamomi) Stem-end rot (Phomopsis sp .. Dothiorella sp.) Fruit rot (Dothiorella sp .) Anthracnose (Colletotrichum gloeosporioides) Leaf tip-burn (various causes. not all disease related, including salt accumulation from overfertilizing) Algal leaf spot (Cephaleuros virescens) Scab (cause unknown; resistant varieties are available) Insect Pests of Avocado Red-banded thrips (Selenothrips rubrocinctus) Armored scales (several species) Chinese rose beetle (Adoretus sinicus) Fruit fly Mites Black twigborer (Xylosandrus compactus) Mealybug (Dysmicoccus neobrevipes, Nipaecoc-cus nipae) Plantbugs (Hyalopeplus pellucidus and other species) The authors would like to thank Drs. R A Hamilton, R F. L. Mau, H. Y. Nakasone, W. Nishijima, and E. Trujillo for their comments and suggestions on tAe manuscript. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Noel P. Kefford, Director and Dean, Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawaii at Manca, Honolulu, Hawaii 96822. An Equal Opportunity Employer providing programs and services to the citizens of Hawaii without regard to race, color, national origin, or sex. 11 /87 

English

Avocado

Cooperative Extension Service CTAHR Fact SheetHorticultural Commodity no. 4*January 1997*Replaces HITAHR Commodity Fact Sheet AVO-3(A).Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Charles W. Laughlin,Director and Dean, Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, Honolulu, Hawaii 96822. AnEqual Opportunity / Affirmative Action Institution providing programs and services to the people of Hawaii without regard to race, sex, age, religion, color, nationalorigin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status.Family: LauraceaeScientific name: Persea americana Mill.Origin: American tropicsDescriptionAvocado is a much-branched evergreen tree 40–80 fttall with elliptic leaves 3–10 inches long. Its flowers aresmall, greenish, and perfect (having both male and femaleparts). The fruits are round, pear shaped (pyriform), oroblong, with green, yellow, reddish purple, purple, or blackskin varying from pliable to woody and from smooth torough and pebbly. The fruit flesh is greenish yellow tobright yellow when ripe, with a buttery consistency. Fruitshave a single large seed making up 10–25 percent of thefruit weight.VarietiesAvocado trees vary in size and adaptability to climateand soil type. They also vary in length of time from flow-ering to fruit maturity and, therefore, in season of matu-rity. Fruits of avocado varieties, or cultivars, vary widelyin moisture and oil content, from less than 5 percent oil(with a watery texture) to more than 30 percent oil. Fleshtexture should be smooth, but inferior varieties often havefibrous strings embedded in the flesh. Fruit weight rangesfrom about 1/4 lb to more than 3 lb. Three horticultural racesare recognized: Guatemalan, West Indian, and Mexican.Many cultivars are hybrids between races and are notreadily identifiable by race. Most cultivars grown in Ha-waii are of the Guatemalan race, or are hybrids betweenthe Guatemalan and West Indian races.PropagationSeedling plants fail to reproduce true to type, and graft-ing is necessary to maintain desired growth, bearing, andfruit characteristics. Grafted trees usually begin to bearfruit three to four years after transplanting. To avoidPhytophthora root rot contamination in the nursery whengrowing seedling root stocks for grafting, (1) do not useseed from windfall fruits picked from the ground, (2) propa-Avocadogate seedling rootstocks in sterilized, disease-free media,and (3) do not allow containers to contact soil. Purchaseonly plants that have been grown with these standards ofsanitation.Soil typesAvocado trees grow well on many soil types providedthe soil is well drained. Planting sites should not have lowareas where water stands after heavy rains. Poor soil drain-age and soil pH less than 6.2 (acid soil reaction) favor de-velopment of Phytophthora root rot.LocationAvocado trees are sensitive to sodium chloride andtherefore are not suited to shoreline planting. Areas ex-posed to high winds should be avoided because branchesare easily broken, and flowers and fruits may be damaged.Relative humidity of 50 percent or more is desirable dur-ing flowering and fruit set, so production in dry areas maybe low.There is a great deal of variation among hybrid culti-vars in adaptation to different elevations and temperatures.In Hawaii, Guatemalan and Mexican races and their hy-brids tolerate cool upland conditions and can be grown upto elevations of approximately 2000–2500 ft. Varieties ofpure Mexican parentage, rarely grown in Hawaii, can begrown up to the frost line. The thin-skinned West Indianvarieties, locally known as “summer pears,” usually pro-duce fruit of marginal quality when grown above 1000 ft.Cultural practicesTrees should be spaced 25–30 ft apart. Cultivation forweed control should be avoided by using herbicides; ifpracticed, cultivation should be as shallow as possible toavoid damage to the shallow avocado root system. Organicmulches are recommended for weed control and mainte-nance of good soil condition. Pruning trees is usually un-necessary except to shape young trees and remove deadbranches. Heavily laden fruiting branches may be proppedwith poles.2CTAHR Fact Sheet HC–4 Avocado CTAHR — January 1997  Important plant nutrients applied as fertilizer to avo-cado are nitrogen (N) and calcium (Ca). Among the mi-cronutrients, zinc (Zn) is important to avocado and shouldbe applied whenever deficiency is indicated. If the soil isstrongly acidic, add calcium carbonate to raise pH to 6.2.If soil pH is adequate (pH 6.2–6.5), use calcium nitrate toprovide calcium without increasing pH.PollinationPollination is principally by bees. Two avocado flow-ering types, A and B, are distinguished by what time ofday the flowers open. Each flower opens twice and is func-tionally female (pollen receptive) at first opening and func-tionally male (pollen shedding) at second opening. Type Aopens first in the morning, closes about midday, and re-opens in the afternoon of the following day. Type B opensfirst in the afternoon, closes in the evening, and reopensthe following morning. Having trees of both types is im-portant in orchards because production is improved byadequate cross-pollination (see Table 1). This is not asimportant in residential areas, however, where both treetypes are usually present. Avocado trees flower during latewinter and early spring in Hawaii. After fruit is set, somepremature fruit drop is common and can be expected.HarvestingFruits are picked when mature but still hard and thenallowed to ripen. Mature fruits are full sized, may changecolor slightly or lose glossiness, and have brown seed coats.Determining maturity may be difficult and usuallyrequires experience. Fruit should be harvested from thetree with pruning shears or special clippers and never pulledfrom the branch. The pedicel (fruit stem) should remainattached to the fruit. When the stem is pulled out, the fruitoften spoils. Fruits are easily bruised, and windfall fruitsare not marketable.PostharvestFruit ripens only after falling or being picked. Ripe-ness is indicated by softening of the fruit. Fruit picked tooearly tends to shrivel and may fail to ripen. Determiningthe ripeness of thick-skinned varieties by feeling for soft-ness may be difficult and requires some experience. Some-times the pedicel is removed and a toothpick inserted totest fruit softness, but this method may permit entry ofdisease organisms. Fruit of some cultivars may be refrig-erated without damage for several days after ripening.Diseases of avocadoDodder (Cuscuta sandwichiana)Avocado root rot (Phytophthora cinnamomi)Stem-end rot (Phomopsis sp., Dothiorella sp.)Fruit rot (Dothiorella sp.)Anthracnose (Colletotrichum gloeosporioides)Leaf tip-burn (various causes, not all disease-related, in-cluding salt accumulation from overfertilizing)Algal leaf spot (Cephaleuros virescens)Scab (cause unknown; resistant varieties are available)Insect pests of avocadoRed-banded thrips (Selenothrips rubrocinctus)Armored scales (several species)Chinese rose beetle (Adoretus sinicus)Fruit flyMitesBlack twig borer (Xylosandrus compactus)Mealybug (Dysmicoccus neobrevipes, Nipaecoccus nipae)Plantbugs (Hyalopeplus pellucidus and other species)C. L. Chia and D. O. EvansCTAHR Department of HorticultureTable 1. Avocado varieties recommended for home gar-den plantings in Hawaii.Flowering typeSeason of bearing  A  BFall and winter San Miguel CaseSemil-34 KahaluuWinter and spring Greengold NishikawaHayes SharwilSpring and summer Ohata ChangMurashigeSource: HITAHR Brief 052, “Recommended fruits and nuts for the home garden.” The authors thank Drs. R A. Hamilton, R. F. L. Mau, H. Y. Nakasone, W.Nishijima, and E. Trujillo for their comments and suggestions on the manu-script.

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Avocado

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