Most of our favorite vegetables -- beans, peppers, potatoes, and tomatoes (technically fruits!) -- are annuals. They complete their life cycles in a single growing season, so we have to plant them year after year. There aren't many true perennial vegetable garden plants, but there are some that behave like perennials. Here are seven to keep you stocked with edibles for many seasons.
This member of the thistle family produces large, attractive perennial vegetable plants. If the edible flower buds (what we eat as artichokes) are not harvested, they unfurl to reveal fuzzy purple flowers. Grow artichoke (Cynara scolymus) in full sun and moist, well-drained soil. Artichokes require ample, consistent moisture for best growth. They survive drought but don't produce as well in dry conditions. Start artichokes from root divisions (preferred method) or seeds (seed-grown plants typically don't produce as well as root divisions). Plant 24-36 inches apart in rows about 36 inches apart. Amend the soil prior to planting with 2 inches of compost. Fertilize monthly with a high-nitrogen fertilizer. When growing artichoke as a perennial, amend the soil around plants each spring with a 1- to 2-inch layer of compost. Where marginally hardy, cut back the plant in fall and cover with a 6-inch-thick layer of straw. Harvest perennial artichokes in spring, with a secondary peak in fall. Harvest the flower buds when the stalk has fully extended but the bud has not opened. Err on the side of early harvest rather than late to avoid woodiness in the heart. Marginally hardy in Zones 6-7; hardy in Zones 8-10.
This hardy crop lasts for decades in the garden and is one of the first vegetables that can be harvested in spring. Plant asparagus (Asparagus officinalis) in full sun and moist, well-drained soil. Mix a 2-inch-thick layer of compost into the planting site. Because asparagus is long-lived, it's important to adequately prepare the soil before planting. Grow asparagus from rooted crowns, available from garden centers and online. A month before the last frost in early spring, dig trenches 6 inches deep (in clay soil) or 8-10 inches deep (in sandy soil). Space the trenches 36 inches apart. Add a phosphate fertilizer to the planting trench according to package directions. Avoid fertilizers high in nitrogen, which will promote foliage over stalk production. Set the root crowns 12 inches apart in the trenches. Cover the crowns loosely with about 3 inches of soil. After the new plants grow for about six weeks, add another 3 inches of compost-enriched soil. Finish filling the trench in fall. Hand-weed to avoid damaging plants. Leave asparagus unharvested the year you plant it so it becomes well established in the garden. In the second year after planting, harvest for only two weeks. By the third year, harvest for the usual five to eight weeks. Start harvesting when the spears are 1/2 inch in diameter. Harvest every day in warm weather and about every three days in cool weather. Every year, leave some of the spears to grow into fernlike plants that rejuvenate the roots for next year's crop. Zones 4-8
In the same family as sunflowers, Jerusalem artichokes (Helianthus tuberosus, also called sunchokes) are grown like potatoes for their underground tubers. You can eat them raw or cooked like potatoes. However, because their carbohydrate breaks down to fructose instead of glucose, Jerusalem artichokes can be a better choice than potatoes for people with diabetes. Plant the tubers as soon as the ground can be worked in spring in fertile, well-drained soil and full sun. Place them 3-5 inches deep in rows 36-42 inches wide and leaving 15-24 inches between plants. Hand-weed to avoid disturbing the plant while it is growing. By August, it will be more than 6 feet tall with yellow flowers. Tubers about 4 inches long and 3 inches in diameter begin to form in late summer. Wait until after frost to harvest. Handle them carefully as the skin of the tubers is very thin. You can leave some tubers in the ground to grow into plants again the following spring. Zones 4-9
Note: These are vigorous plants that spread by underground rhizomes and may become difficult to eradicate. Some gardeners consider them invasive.
Onion Family Members
Some types of onions, such as the fall-planted bunching and Egyptian onions, continue to produce new onions even when some are harvested. Grow all onions in full sun to partial shade in well-drained soil that is high in organic matter. In spring, apply fertilizers high in phosphorous and potassium but low in nitrogen. Plant onions as sets, seeds, or transplants in spring as soon as the ground can be worked. Space them 6 inches apart, in rows about 1 foot apart.
Transplants should be placed about 1 inch deep. Bunching onion (Allium cepa var. solanium, also called the Welsh onion) is a type of multiplier onion. It does not grow into large bulbs. Both the roots and tops can be eaten, but some may be left to grow into larger onions. The Egyptian onion (Allium cepa var. viviparum) produces small bulbils at the top of its stalk in late summer. You can use these tiny onions as they are, or plant them in the fall to grow more Egyptian onions. Garlic chives (Allium tuberosum) grow similar to chives (Allium schoenoprasum), with slender leaves up to a foot long and star-shape white flowers in late summer. Both garlic chives and chives form clumps fairly rapidly. Zones 4-8
This sharp-flavor vegetable is technically a hardy biennial, meaning it grows for two years. It is a type of chicory and is related to Belgian endive. Dark red leaves with white veins form into a tightly clumped head that resembles cabbage or romaine lettuce. Grow radicchio (Cichorium intybus) in fertile, well-drained soil in full sun. Sow seeds in spring or autumn, then harvest the inner heads in late fall when they are firm and have the deepest color of white and red, leaving the roots in the ground to produce another crop. Avoid picking it too early; immature leaves taste bitter. Add olive oil and salt to the fresh leaves to cut the bitter flavor. Zones 4-8
Though many people treat it like a fruit, rhubarb (Rheum rhabarbarum) is actually a hardy perennial vegetable (because you eat the stems, not the plant's fruits). Plant rhubarb in full sun and moist, well-drained soil. Locate it where it won't be disturbed because it will be productive for many years. Plant crowns in early spring as soon as the ground can be worked. Place the central bud 2 inches below the soil line. Space the crowns 6 feet apart. Spread a 2-inch-thick layer of compost around new plants when the air temperature rises above 80 degrees F. Cut off at the base of the plant any flower stalks that develop. Apply a balanced fertilizer in early spring. After harvest, spread a 2-inch layer of compost around plants. When the stalks become thin, usually after six to eight years, dig and divide the plant in spring or fall. Rhubarb stalks have the best color and flavor when harvested during cool weather. Leave first-year plants unharvested. By the third year, harvest all stalks larger than 1 inch wide for as long as eight weeks. Use only the stems; the leaves contain oxalic acid and are poisonous. Zones 2-9
Sorrel is a perennial herb with a tart, lemony flavor used for soups, stews, salads, and sauces. The two main sorrels grown are common sorrel, Rumex acetosa, and French sorrel, Rumex scutatus. They are relatives of rhubarb, and the leaves contain small amounts of oxalic acid that's not harmful when consumed in small quantities. The leaves are a good source of vitamin C. Sorrel tastes best in early spring; it becomes bitter as the weather warms. It's hard to find in markets because it wilts shortly after harvest. To grow sorrel, sow seeds directly in the garden in full sun and average soil 6-8 inches apart in rows 2 feet apart. Established plants may be divided. Garden sorrel is frost-hardy to Zone 5; French sorrel is hardy to Zone 6.