Vegetable Classifications

Vegetables can be classified in many ways, but the two most useful ways to gardening are by their growth habit and their temperature requirements. Vegetables are generally classified as annual or perennial crops based on whether they must be replanted each year or will produce crops for multiple years before replanting.

Most vegetables are considered annual crops. Common perennial crops are artichoke, asparagus, rhubarb, and many herbs. Consider the long-term space and cultural needs of these crops when planning your garden.

Most vegetables are further classified as cool-season or warm-season crops based on the temperature range in which they grow best and produce the best-quality crops. Consider this when deciding when to plant and harvest crops in the garden. Planting a particular vegetable should be timed so that it grows and matures when normal temperatures are ideal for it to produce a good-quality crop.

Cool-Season Vegetable Crops

Cool-season vegetables grow best and produce the best-quality crops when average temperatures are 55° to 75°F, and they usually tolerate slight frost when mature. Some crops (notably broccoli, celery, carrot, lettuce, onion) in this group are subject to bolting (premature flowering and seeding) if temperatures are too warm as the plant is maturing. The food value of cool-season vegetables is usually higher per pound and per square foot than that of warm-season vegetables, because the edible parts of the plant are the vegetative parts, such as roots, stems, leaves, or immature flower parts, rather than the fruit. Compared with warm-season crops, cool-season crops generally have shallower root systems, show more dramatic response to nitrogen and phosphorus fertilization, store best at a temperature just above 32°F, and are not susceptible to chilling injury after they are harvested.

Examples include: 

• roots: beet, carrot, parsnip, radish, turnip
• stems: asparagus, white potato
• leaves: cabbage, celery (fleshy petioles), lettuce, onion, spinach
• immature flower parts: broccoli, cauli-flower, globe artichoke

Warm-Season Vegetable Crops

Warm-season vegetables require long hot days and warm soil to mature. They grow best and produce the best-quality crops when average temperatures are 65° to 95°F, and they are intolerant of prolonged freezing temperatures. The food value of warm-season vegetables is usually lower per pound and per square foot than that of cool-season crops because the fruit of the plant is eaten. Many warm-season vegetables are actually immature or mature fruits. In other words, vegetables such as tomato and squash are fruits in the botanical sense, just as oranges are a fruit.

Examples include:

• mature fruits: cantaloupe, winter squash, tomato, watermelon
• immature fruits: sweet corn, snap and lima beans, summer squash