Rhubarb

Garden rhubarb is a hardy perennial that grows 2 to 4 feet (61 to 122 cm) tall, with large leaves and thick red or green stalks. Stalk color depends on the variety. A well-kept plant can stay in the garden for 10 to 15 years. The stalks are the part used in pies, sauces and jams.

Rhubarb is almost always planted from crowns, which are cut pieces of an established plant with a leaf bud on top and healthy roots below. Plant crowns in early spring; in Iowa, spring is the best time to plant.

Set each crown so the leaf bud sits about 1 inch (2.5 cm) below the soil. Other guides give 1 to 2 inches (2.5 to 5 cm) or about 2 inches (5 cm). Cover the crown with no more than 1 inch of soil, press it firmly, and water well.

Space plants 3 feet (91 cm) apart, and keep rows 4 feet (1.2 m) apart if you plant more than one row. Choose a full sun site, with at least 6 to 8 hours of direct sun a day. Avoid shady spots near trees and shrubs.

Rhubarb can be grown from seed, but it is usually propagated by division of the crown. If you start seed, soak it for 2 hours, then sow in individual pots 5 to 7 weeks before the last frost, covering the seed about ¼ inch (0.6 cm) deep. Thin to one seedling per pot and plant out after the danger of frost has passed.

Watering. For the first 2 to 3 years, water one to two times a week so moisture reaches the root ball. After year three, water every 1 to 2 weeks, soaking the soil 12 to 18 inches (30 to 46 cm) deep. Mulch with straw, grass clippings or bark to hold moisture and limit weeds.

Feeding. In early spring, before the leaves emerge, scatter about ½ cup (120 ml) of all-purpose garden fertilizer around each plant and work it lightly into the soil, keeping it off the crown. Don’t fertilize during the first year.

Flowers. Remove flower stalks as soon as they appear, because flowering reduces plant vigor. Old plants tend to flower more than young ones.

Dividing. Divide established plants every 5 to 10 years. Another guide suggests every fourth or fifth year.

Rhubarb is rarely troubled by pests or diseases when it is healthy and well watered. Over-watering or wet soil can cause root rot. The rhubarb curculio, a beetle, can puncture stalks and cause minor damage. Phytophthora crown or root rot is a serious but uncommon disease that causes sunken lesions at the base of the stalks and a collapsed plant. Slugs may be a problem in moist areas.

Don’t harvest any stalks during the first two years after planting. In year three, harvest for 3 to 4 weeks; after year four, harvest for 6 to 10 weeks. Another guide gives 8 to 10 weeks, ending around mid-June in Iowa.

Pick stalks when they are 10 to 15 inches (25 to 38 cm) long. Grasp the stalk near the base, then pull up and to one side; never cut stalks at the base of the plant. Leave about one-third of the stalks on the plant at any time. A plant yields about 4 to 12 pounds (1.8 to 5.4 kg) of stalks a year.

Stalks kept in a plastic bag in the refrigerator last 2 to 4 weeks; another guide says 1 to 3 weeks. To freeze, blanch stalks in boiling water for 1 minute and cool them in ice water. Frozen stalks keep for up to a year; another guide says up to 6 months.

Don’t eat the leaves; only the stalks are edible. The leaves are toxic because they contain a high level of oxalic acid. People prone to kidney stones are advised to avoid rhubarb. Rhubarb is listed as toxic to both dogs and cats.