THE KIWIFRUITI

James A. BeutelExtension Pomologist, University o£ California, Davis

INTRODUCTION

Kiwifruit {Aatinidia ohinensis) is a large subtropicalvine that bears fuzzy, brown-skinned fruit with an emerald greenflesh. Botanically, the fruit is similar to a tomato or goose¬berry. It is a berry that has many of its cells filled withsmall, soft, black seeds. Similar in size and shape to a lemon,the fruit is sold and served fresh as an appetizer, in dessertsand beverages, and with salads, fish, poultry, meats and breads.Jt also can be processed as frozen or canned fruit. A kiwifruitcontains as much ascorbic acid (vitamin C) as a large orangeand is low in calories. Because it contains an enzyme thatbreaks down protein, kiwifruit also can be used as a meat ten-derizer.

COMMERCIAL PRODUCTION AND COSTS

Kiwi vines are grown commercially today in New Zealand andCalifornia. Israel, Greece, Italy, France, Japan, and the southeastern United States currently are looking at kiwifruit as apotential new crop for their respective areas.

New Zealand began commercial production of kiwifruit inthe late 1950s and today has 2000 bearing acres. By 1983 itexpects to have 3000 bearing acres. (Normally, kiwi vines donot attain a commercial level of fruit production until theirfourth year of growth.) In 1976, California had 80 acres ofcommercially bearing vines which produced 250 tons of fruit.California could be producing as much as 500 tons of fruit percrop by 1983-85 if its current total 1500 acres of kiwi vinesare then in full production. Based on current marketing con¬siderations, such a level of production could easily knockdown today's $1 per pound net for California growers to 20-30<|:per pound.

Production of kiwifruit on a per acre basis in Californiahas averaged 1 to 3 tons for 4-year-old vines, 3 to 5 tons for5-year-old vines, and 5 to 9 tons for vines 8 to 12 years old.

Costs to establish one acre of kiwifruit are approximately$800 to $1200 for plants, $1000 and up for trellises, $400 to$1500 for an irrigation system, and $800 to $1600 for the four

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years of care before the vines become commercially productive.Thus, to establish one acre of kiwifruit requires an investmentof $3200 to $5300, not including the cost of the land. Annualcosts to maintain bearing kiwi vines run about $600 per acrefor cultural labor and materials plus interest on the investment.

CULTURAL CONSIDERATIONS

Climate

The kiwifruit is native to the Yangtze Valley in SouthChina, It grows there at elevations around 3000 feet whereheavy summer and winter rains are common.

The main kiwi vine production area in New Zealand is theBay of Plenty (Tauranga) which has a mild climate: 90°F maximumand 30°F minimum temperatures with SO to 100 inches of rainfallspread over the entire year. In California and Mediterraneanareas where summers are hot and dry, the water needs of the vinesare supplied by irrigation.

California's main production areas are: Chico-Gridley-Yuba City, Lodi-Modesto, Fresno-Reedley-McFarland, Fallbrook-Escondido, and Ventura-San Luis Obispo plus Watsonville. Kiwivines can be grown in other areas, but it should be noted thatintense summer desert heat or cold winters or frosts after March15 and before November 15 restrict their growth and fruiting.New growth and fruit on the vines can tolerate 30°F to 105°F.The dormant vine can withstand temperatures as low as 10®F iffully dormant but only 24°F when partially dormant in the fall.

Hard, dry desert winds as well as persistent, cool coastalwinds can damage kiwi plants by scarring fruit, breaking shootsand tearing up large leaves on the vines. Where winds occur,windbreaks of poplar. Eucalyptus or conifers are required inorder to obtain good plant growth and quality fruit. (New Zealand'sexperienced kiwi vine growers provide their plantings with excellentwind protection.)

Soil

Kiwi vineyard soil should be loamy sand to loam in textureand 4 to 8 feet deep for good root growth. (New Zealand hashad higher yields than California, 7 to 9 tons per acre on maturevines, mainly because its soil is deep and well drained.) Landthat is good for almonds, peaches, avocados and other crops whichrequire deep, well-drained soils is usually satisfactory for kiwivines. Soils used for permanent pasture are not satisfactory forkiwi vines. Kiwi vineyard soils should be low in salts (sodiumand chloride) and neutral to acid in pH so that iron cholorosiswill not be a problem.

Irrigation

Normally, kiwi vines require frequent irrigation, usuallyweekly during their first three years of growth. Water can beapplied for furrow, drip or overhead sprinkler irrigation.Water used to irrigate kiwi vines should be low in total salts,probably below 700 parts per million (ppm) where furrow irrigatedand less than 300 ppm if irrigated by overhead sprinklers.

Fertilization

Generally, the main nutrient that must be applied to Calif¬ornia soils to grow kiwi vines is nitrogen. Small quantitiesof nitrogen are applied the first year. Ultimately, 150 poundsof nitrogen per acre must be applied for bearing vines. Whenplants are young, it is best to apply a fertilizer such as ammon¬ium sulfate about three times per year (January, April and June)using 1 oz. per plant each application. This amount should beincreased to 2 oz. per plant the second year and to 4-8 oz. perapplication the third year.

Propagation

Kiwifruit vines can be propagated by grafting seedlingsor by rooting cuttings. Both methods can be used to produceequally good vines and crops.

Grafting seedlings. Seeds for planting can be extractedfrom any ripe kiwifruit by peeling fruit and running it througha blender at slow speed to separate the seeds from the pulp. Byslowly washing the slurry of pulp and seeds in a bowl or pan,the water will float away the pulp and leave the seeds in thebottom of the container. The seeds can be dried for storage.When needed, the seeds are placed on a wet paper, wrapped in aplastic bag, and placed in a refrigerator for three weeks tostratify so that they will germinate uniformly. Next, the seedsare planted in sterilized soil. They will germinate in threeweeks at 65-7S°F. Then they are planted in 3 or 4 inch pots andgrown at 60-75°F. When they are 3 inches high and frost is past,they can be planted 12 inches apart in nursery rows spaced 3 feetapart. One-year-old seedlings can be whip grafted in Januaryor April with dormant wood. Budding (T-bud) also is satisfactoryin April or May if dormant wood is used.

Rooting cuttings. Cuttings are made from inch-diameterwood taken in midsummer. Each cutting is two to three nodeslong (5-8 inches). A whole leaf is left at the top node, andthe leaves are removed from the bottom nodes of each cutting.The basal end of the cutting is dipped in 4000-8000 ppm indole-

butyric acid (IBA) rooting hormone solution or 4% naphthaleneacetic acid or equivalent rooting powder. The cuttings areset in a course rooting medium (perlite or h perlite:% vermiculite)and placed under intermittent mist (water spray). Rooting occursin 6 to 8 weeks at 70-75®F. The rooted cuttings are transplantedinto pots and returned to a humid greenhouse or mist to minimizetransplant shock. (Rooting the cuttings in 4-inch deep potsavoids an otherwise necessary first transplanting.) Well-established plants in pots can be transplanted to the fieldnursery or to 1 to 3 gallon containers. When plants are inchin diameter or 4 feet tall they have reached minimum size fortransplanting to the permanent kiwi vineyard. Transplantingcan be done bare root in the winter or from containers in thewinter or spring.

Dormant cuttings can be rooted in the winter : ' given a24-hour soak in 200 ppm IBA or dipped in 4000 IBA S- ution orrooting powder. They are set in a course medium, given bottomheat, and the tops are left at an air temperature of 30-40®F.The cool tops prevent growth until the bases of the cuttingsare rooted in the heated medium. After rooting is complete,the cuttings are transplanted to containers and placed in ahumid house for further growth. Later, they can be moved tolarger containers or to a field nursery.

Vineyard Planting

Kiwi vines are planted 20 feet apart in rows 15 feet apart,giving a total of ISO vines per acre. Individual kiwi vines beareither female or male flowers, so cross-pollination is necessary.Normally, about 101 of the vines planted are males, spaced everythird vine in every third row. Female vines are all Haywardvariety, and males may be Chico-male, Matua, or Tamori. Honey¬bees provide 'the necessary pollination, using 3-4 hives per acre.

Trellises

Plants in each row are supported by a sturdy 6-foot-hightrellis. The trellis is made of 4-inch-diameter posts with 2x6inch cross arms that are 5 to 6 feet long and covered with threeto five 11 or 12 gauge wires. Each vine is trained as a singletrunk to the top of a 6-foot-high post where it is headed sothat two arms or cordons develop from the trunk along the centerwire. Fruiting canes grow out from the center cordon and areallowed to hang over the outside wires. Fruiting canes areremoved after fruiting for 1 or 2 years and replaced by new onesfrom the central cordon. Failure to prune results in uncontrolledgrowth, small fruit size, alternate bearing, and eventually poorcropping.

PESTS AND DISEASES

To date, pests and diseases of kiwi vines in Californiahave been few, but as crop acreage increases, more of theseproblems are expected to develop. Omnivorous leaf roller wormshave damaged fruit, and caterpillars occasionally will causeextensive leaf damage. Worms moving from vineyards into kiwiplantings cause the most damage. Currently, chemical sprayingto control worms is limited by the lack of registered materialsfor bearing vines. (In New Zealand, tortrix worms require foursprays per year.]

Soil-borne nematodes attack vines and can retard theirgrowth. Root-knot and lesion nematodes are both serious pestsof kiwi vines, but they can be controlled by good soil fumigationprior to planting.

Diseases sometimes encountered are crown rot {Phytophthoraspecies) and oak root fungus (Armillaria mellea). Crown rotoccurs when vines are planted on clay soils or planted too deep.Oak root fungus affects vines wherever it occurs in soils.

HARVESTING

California kiwifruit is picked in November. New Zealandharvests its fruit in May. All fruit on a vine matures at thesame time and can be harvested in a single pick.

When mature, the fruit contains about %% sugar and a moderateamount of starch. The starch changes to sugar during storage,so kiwifruit, when eaten, runs between 12 and 15^ sugar. A large(100 gram) kiwifruit contains 60 to 70 calories. Its vitamin Ccontent is 90 to 105 milligrams.

STORAGE

Fresh, mature kiwifruit can be stored from 4 to 6 monthsat 31-32°F if protected from moisture loss by placing it in apolyethylene-covered pack. Botrytis and other storage moldsand rots often cause decay in stored fruits, and present methodsfor controlling them are not fully satisfactory. Fruit is normallypacked in a one-layer flat. Six or 7 pounds of fruit are placedin each flat, according to size: e.g., 25, 30, 40, and 48. Forbest storage, fruit should be cooled to 30-36°F the day they arepicked and packed later, keeping the temperature as near 32®F aspossible after packing.