Vitis vinifera L.

Vitaceae
Old World, European or Californian grapes

Uses

Grape seeds contain 6–20% oil, used for edible purposes, soaps, and as a linseed substitute. The leaves of this and other species are eaten in other cultures.

Cultivation

Grapes are propagated from cuttings, field-budding or graftings to resistant rootstocks, such as 'Rupestris St. George', 'Aramon X Rupestris No. 1', 'Solonis x Othello 16131, 'Dogridgel or 'Salt Creek'. Prepare area to be planted to grapes by plowing to 25 cm and providing organic matter in soil, by turning under a cover crop or green manure. Grapes are set in either fall or spring. If in spring, plant early to give plants long growing season. Fall planting is unwise in northern regions. Damage from heaving may occur with fall-planted vines. Most commercial vineyards are set 3.6 m with 1-year old plants. In California plant spacings range from 1.8 to 2.4 m x 3.6 m, using 1350 to 1025 vines/ha, respectively. Plant vines about same depth as they grew in nursery, and prune them to a single stem with 2 or 3 buds. Trellis or posts with wires are necessary to train vines. Do not set vine too close to a wooden post, as the post will be disturbed when post has to be replaced. Plant 2 plants in space between posts. if concrete or steel posts are used, the grape hoe is easier to use if a vine is set at each post and one in between. Set vines directly under trellis. Vines out of line may be constantly injured by cultivation. Training and pruning vary with different kinds. Pruning, a very important practice, has a direct relationship to larger yields, higher quality and more uniform production. Vineyards are normally cultivated in spring and early summer in order to stimulate growth. Cultivation should be shallow, only 7.5–10 cm deep. If erosion is a problem, cultivate only enough to prevent weeds from becoming a problem. Leave trash and some growth on land and have some pockets to catch water in soil. Growth of vines may be restricted by seeding a fast growing cover crop which will compete for nutrients and moisture. Since grapevines often outlive those who plant them, and will grow and produce indefinitely with good care. Where manure is readily available, 25–75 MT/ha may be incorporated into the soil. If chicken manure is used, since it is richer in quickly available nitrogen, only one-third to one-half is required. Maintaining organic matter in soil may be aided by growing and turning under cover crops, weeds, hay or straw. Minor elements may be needed to prevent chlorosis, as borax, magnesium sulfate or ferrous sulfate. Fertilizer should be used primarily as a supplement to, not a substitute for, good culture and organic matte. Girdling of canes is often used to concentrate carbohydrates in fruit.

Harvesting

Stage of maturity for harvesting depends on the use to be made of fruit, such as jelly, juice, or wine. Guides to proper stage of ripeness are: taste (greenest grapes of cluster should be tested), color, aroma, changing of stem from green to brown, shriveling of stem, softening in texture of pulp, thickening of juice and etc. Do not pick too early. Much weight is lost by picking too early and fruit is not so sweet. The longer grapes remain on vine (within reason) the higher the sugar content. Acidity is important to taste and to wine-making quality. In California type grapes, sugar-acid ratio gives a better measurement of quality than either factor alone. Grapes do not gain sugar after picking. As grapes do not mature evenly, they must be gone over 2 or more times to get most of crop harvested at proper stage of maturity. Careful handling of fruit is necessary for table use of grapes. Cut grape clusters from vine, pick off green and damaged fruits and place gently in picking baskets. Grapes should not be picked when wet, or during very hot weather, as they decay quickly. Mechanical pickers have been devised and some vineyards are especially trained for their use. Vinifera type grapes are usually packed by the 'stems up' method, starting at one (lower) side of a tilted box. They are usually shipped in display lug boxes, 5 3/4" x 13 1/2" x 16 1/8. Grapes for juice or wine are sold in bushel containers or wooden lug boxes. Good fruit of good varieties may be stored for 3–6 months; usually held at -1° to -0.5°C, with relative humidity of 85–95%, depending on air velocity. Fumigation with 1% sulfur dioxide before storage and refrigeration with 0.2% of the gas at 10-day intervals helps prevent decay. Grapes picked before rains usually keep better than those picked after rains. Grapes for raisins are of Vinifera type. In California and Arizona about 90% of raisins are sun-dried between the rows of vines; elsewhere dehydrators are used.

Description

Perennial, woody climbing vine; stems up to 35 m long, but in cultivation usually reduced by annual pruning to 1–3 m; leaves thin, circular to circular-ovate, 5–23 cm broad, margins dentate or jagged, basal sinus deep and lobes often overlapping, 5–7-lobed, glabrescent above, often with persisten tomentum beneath; tendrils branched, normally opposite 2 leaves out of three; flowers numerous, in dense panicles or thyrses opposite leaves; flower clusters and tendrils absent at every third node; calyx very shortly 5-lobed; petals about 5 mm, pale green, sweet-scented; fruit a soft, pulpy berry, skin adhering to pulp, oval or oblong, ellipsoid to globose, skin green, yellow, red or purplish-black, in large, long clusters; seeds 2–3, sometimes none, pyriform, with rather long beak.

Yields and Economics

Maximum productivity of a vine depends largely upon the vigor of the vine the preceding year. In California average yields vary from 25 to 30 tons/ha. California produces 90% of United States grapes. United States exports grapes to Canada, Venezuela, Philippines, and United Kingdom; imports from Chile, Canada, and South Africa. Production in United States is about 3.5 million tons annually, with an average price in 1967 of $.72/kg.

Ecology

Requirements are for long, warm to hot dry summers and mild winters. Plant damage occurs at -18°C; frost kills young shoots. Daily mean temperature should be at least 18°C. This species will not endure the high temperatures coupled with high humidity of tropics. Humidity promotes disease. In United States this grape is grown in California and Arizona, but will not tolerate the cold winters and humid summers of eastern United States. Grape culture is best where there is no rain between blooming and harvesting. Rain is desirable in winter but now in spring or fall. Irrigation is desirable and often essential; several irrigations may be necessary, beginning in spring when available water in soil has been used, and continuing until harvest; perhaps later in very hot regions. Sandy or gravelly clay loams are most desirable, as they provide good drainage. Soil fertility is not so important as soil structure. Vitis vinifera is reported to tolerate annual precipitation of 0.9 to 27.2 dm (mean of 12.1 cases = 134) annual temperature of 8.3 to 28.5°C (mean of 21.8 cases = 133) and pH of 4.5 to 8.7 (mean of 6.8 cases = 66).