AMES, Iowa — Rhubarb, classed as a vegetable, is used as a fruit because its high acidity gives it a tart flavor. Iowa State University horticulturists make rhubarb planting recommendations for gardeners planting their first rhubarb patch and those maintaining an established planting. Gardeners with additional questions should contact Hortline at 515-294-3108 or firstname.lastname@example.org.
Rhubarb performs best in well-drained, fertile soils that are high in organic matter. Work the soil deeply (12 to 15 inches) and add liberal amounts of organic matter, such as compost or barnyard manure, before planting.
Rhubarb also requires full sun. The planting site should receive at least six hours of direct sun each day. Avoid shady sites near trees and shrubs.
Spring is the best time to plant rhubarb in Iowa. Plants can be purchased at garden centers or from mail-order catalogs. Digging and dividing large existing plants is another source of plants.
Plants growing in pots should be planted at the same depth as they are currently growing in their pots. Bare-root plants should be planted with the buds 1 to 2 inches below the soil surface.
Dig and divide large plants in early spring before growth starts and as soon as the soil can be worked easily. Dig deeply around the rhubarb clump and lift the entire plant out of the ground. Divide the clump into sections by cutting down through the crown between the buds. Each division should contain at least two or three buds and a large portion of the root system. Replant the divisions as soon as possible.
Rhubarb plants should be spaced 3 feet apart.
The cultivars ‘Canada Red,’ ‘Crimson Red,’ ‘MacDonald,’ and ‘Valentine’ have attractive red stalks and are good choices for Iowa gardens. ‘Victoria’ is a reliable, green-stalked cultivar.
After planting rhubarb, it’s best to wait two years (growing seasons) before harvesting any stalks. The two year establishment period allows the plants to become strong and productive.
Rhubarb can be harvested over a four-week period in the third year. In the fourth and succeeding years, stalks can be harvested for 8 to 10 weeks.