Classification of Vegetables

Vegetables may be classified on the basis of life cycle, edible or economic parts of the plant (use), adaptation, and botanical features.

Life Cycle

Based on life cycle, vegetables may be classified as annuals, biennials, or perennials.

1. Annual: Most vegetable garden crops are true annuals, such as corn (Zea mays), or are cultivated as annuals, such as tomato (Lycopersicon esculentum). These plants are selected for either fall or summer cultivation. They require a few weeks to several months to maturity, depending on the cultivar.
2. Biennial: Few popular vegetable garden crops are biennials, and, even then, they are frequently cultivated as annuals and replanted each season. Examples are sugar beet (Beta vulgaris) and carrot (Daucus carota).
3. Perennial:   Whenever perennial vegetable garden crops are cultivated, they must be strategically located so as not to interfere with seasonal land preparation activities needed for planting annual crops. These plants may be pruned to control growth or to remove dead tissue. Examples are asparagus (Asparagus officinalis) and horseradish (Rorippa armoracia).

Edible or Economic Parts

Vegetables may be operationally classified according to the parts of the plant harvested for food or other uses.

1. Pods: Pods are legumes that are harvested prematurely, cooked, and eaten with the seeds inside. When harvesting is delayed, pods develop fiber and become stringy and undesirable for fresh use. Examples are green bean and okra.
2. Roots: Sometimes primary plant parts (stem root, and leaf) may become modified as storage organs for food. Roots may become enlarged as a result of the accumulation of stored food.
   The roots are dug and eaten baked, boiled, or fried. An example is a sweet potato.
3. Bulbs: Like roots, bulbs are modified stems and leaves, as found in onions. The stem is highly compressed to form what is called a basal plate, while the leaves are storage organs.
4. Tubers: Tubers look like modified roots. The difference between them is that tubers are swollen stems, whereas roots are swollen roots.
5. Greens: Greens are vegetable crops whose leaves are usually picked at tender stages to be used for food. The leaves are generally cooked before being eaten.

Adaptation

Just like fruits, certain vegetable species prefer cool temperatures during production, and others prefer warm temperatures. Based on seasons in which they grow best, vegetables may be classified into two groupings.

1. Cool season:  Cool-season crops require monthly temperatures of 15-18°C (60-65°F). Examples are sugar beet (Beta vulgaris) and cabbage (Brassica oleraceae).
2. Warm season: Warm-season crops prefer monthly temperatures of 18-27°C. Examples are okra (Hibiscus esculentus), eggplant (Solanum melongena), corn (Zea mays), and shallot (Allium cepa).

It should be mentioned that plant breeders have developed cultivars with wide adaptation for many crop species. For example, popular garden crops including corn, tomato, and pepper are grown over a wide range of climates. Even though cultivars with cold or heat tolerance may have been bred for different crops, commercial large-scale production occurs in regions of best adaptation of these crops, unless production is under a controlled environment (greenhouse).

Botanical Features

Vegetables may be classified according to specific botanical characteristics they share in common.

1. Vines: Vines are plants with stems that need physical support; without it they creep on the ground or climb onto other nearby plants in cultivation. Examples are squash, pumpkin, and cucumber.
2. Solanaceous plants: Solanaceous plants belong to the family Solanaceae. Examples are eggplant, tomato, and pepper.
3. Cole crops: Cole plants belong to the Brassica family. Examples are cabbage, cauliflower, and broccoli (Brassica oleraceae var botrytis).