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HORT410 - Vegetable Crops

Olericulture - Vegetable Growing

The field of horticulture is divided into four major categories:

1. Pomology - fruit growing - includes the culture of all fruits and nuts. Grape cultivation, viticulture, is a specialized branch of pomology.

2. Olericulture - vegetable growing - deals with the culture of non-woody (herbaceous) plants for food.

3. Floriculture - flower growing - deals primarily with the cultivation of herbaceous flowering plants and houseplants.

4. Ornamental horticulture - covers the growth of trees and shrubs for use in landscape design, and often with the design and maintenance of gardens, parks, and recreational areas.

Webster's Dictionary defines a vegetable as "a herbaceous plant cultivated for food, as the cabbage, potato, bean, etc; also, the edible part or parts of such plants, as prepared for market or table." Vegetables are generally classified according to the source of the edible plant part(s):

  • root (e.g. beet, carrot, turnip)
  • bulb (e.g. leek, onion, garlic)
  • stem (e.g. asparagus, kohlrabi)
  • flower (e.g. cauliflower, broccoli)
  • tuber (e.g. potato)
  • immature fruit (e.g. cucumbers, green peas, summer squash, sweet corn)
  • mature fruit (e.g. muskmelon, watermelon, tomato, winter squash)
  • leaf (e.g. cabbage, lettuce, spinach)
  • petiole (e.g. celery)
  • seed (e.g. bean)

Note that horticulturally, fruit is defined as the seed-bearing product of a perennial plant. The botanical fruits of annual plants, such as the tomato, melon, eggplant or pepper, are classified as vegetables for horticultural purposes.

Vegetable production for processing (e.g. canning, freezing, or dehydration) is usually distinct from fresh market vegetable production. Whereas vegetables for processing are grown exclusively in the field, a significant quantity of the fresh market production can be in greenhouse structures (e.g. tomatoes, cucumbers, and lettuce). Other specialized areas of the vegetable industry include the production of vegetable transplants and vegetable seed for commercial and home garden vegetable growers. Commercial production of vegetables is supplemented by home garden production; approximately 50% of the families in the U.S. grow some of their own vegetables.

Vegetables are generally cultured as annuals. Exceptions include artichoke, asparagus, cardoon and horseradish, which are grown as perennials. Onions, celery and carrots are typically grown as annuals for consumption, but as biennials for seed production. Propagation of vegetables is mostly by seed, although artichoke is propagated by divisions, Irish potato by tubers or tuber sections, and sweetpotato by rooted shoots.

A number of vegetable crops (primarily those of the Cucurbitaceae) are pollinated by bees (e.g. cucumber, muskmelon, pumpkin, squash and watermelon). Although eggplant, lima bean, okra and pepper will set fruit without bees, bee activity has been shown to increase yields of these vegetable crops. Honey bees do not assist in the pollination of peas, snap bean, sweet corn and tomato, but will collect pollen and nectar from these vegetables.

Vegetables have highly variable climatic requirements. Temperature, water availability, and to a lesser extent day length, are the climatic factors which have the greatest influence on productivity. Cool season vegetable crops (including artichoke, green peas, endive, lettuce, cabbage, cauliflower, broccoli, onions, and spinach) grow best between 12 and 20 C. Warm season vegetable crops (including bean, cucumber, eggplant, muskmelon, okra, pepper, sweet corn, summer squash, watermelon and tomato) grow best between 18 and 28 C. Most cool season vegetables are generally also classified as "hardy" to temperatures as low as 1 C during the juvenile period. Such chilling hardy vegetables include asparagus, broccoli, brussels sprouts, cabbage, garlic, horesradish, kale, onion, pea, radish, rutabaga, spinach and turnip. Warm season crops are generally also classified as chilling tender (sweet corn, snap bean, tomato) or very tender (cucumber, eggplant, lima bean, muskmelon, pepper, pumpkin, squash, sweetpotato, watermelon). The latter are not transplanted or seeded until all risk of frost is over and until soil and air temperature is conducive to optimum growth.

The strict climatic requirements of many vegetable crops have resulted in centralization of production in areas with suitable climate. Because of ocean cooling, California provides ideal conditions for the production of cool season vegetable crops such as lettuce, celery, asparagus, and broccoli during the summer months. A large share of the U.S. lettuce production originates in California.

Rainfall during the growing season was formerly required for successful vegetable production. However, almost all commercially grown vegetables are now raised under irrigated conditions or with supplemental irrigation. In some areas rainfall during certain times of the growing season is detrimental because it interferes with field operations and/or promotes plant disease infection.

Vegetables are generally grown on mineral or organic soils. Sandy loam and loam soils are the preferred types of mineral soils because of the desirable growth conditions and the ease of cultivation they provide, especially for bed preparation and precision seeding. Heavier loams and clay soils are generally avoided because they are not amenable to such cultural practices. Organic soils, sometimes called peats or mucks, are important vegetable growing soils in parts of Florida, New York, Michigan, Wisconsin, and California. Because of their productive capacity, muck soils are often reserved for growing the crops of highest value. Careful management of soil fertility and moisture is critical to ensure the continuous and rapid growth that is necessary for high quality and maximum yield.

The production of vegetables is highly intensive in comparison to the production of field crops such as corn, wheat, and soybean. The greater value of vegetable crops justifies the comparatively high expenditure on labor, irrigation, fertilization, herbicides, insecticides, mechanization, and other resources, including efforts to minimize the use of pesticides through integrated pest management and other sustainable practices. Vegetable production requires considerable hand labor because of the intensive nature of cropping, the variable maturities of plants in a field, and the perishable nature of the harvested crop, especially for fresh market. In recent years considerable advances have been made in both the development of more uniformly maturing plants and mechanical equipment for planting, cultivating, and harvesting vegetables. Perhaps the most notable example of this has been the development of new processing tomato cultivars with characteristics which make them amenable to mechanical harvesting by efficient field harvesters. Virtually all processing tomatoes (those for canning or processing into paste) are now harvested mechanically.

Most vegetables are perishable and maintain peak quality for only a short period after harvest. Cooling (to restrict respiration) and storage in a high relative humidity environment (to prevent desiccation) are important post-harvest handling practices for most fresh market vegetables. A few vegetables (e.g. potatoes and onions) remain in excellent condition for many months with good storage.

Vegetables are of considerable importance in human nutrition. Generally they are rich in vitamins and minerals, low in calories, and they supply bulk and fiber. Some (e.g. beans) are excellent protein sources when combined with other foods. Data on vegetable protein, vitamin, mineral (Ca, P, Mg, Fe, K and Na), fat, carbohydrate, and food energy contents can be obtained from the USDA Nutrient Data Laboratory.

www www.hort.purdue.edu
David Rhodes
Department of Horticulture & Landscape Architecture
Horticulture Building
625 Agriculture Mall Drive
Purdue University
West Lafayette, IN 47907-2010
Last Update: 01/07/08