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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Answers to Frequently Asked Rhubarb Questions

This article was published originally on 5/14/2004

Rhubarb is one of the easiest plants to grow in the garden. While easy to grow, questions invariably arise. Answers to several frequently asked questions are provided below.

Q. Is rhubarb safe to eat after the plants have been exposed to freezing temperatures?

A. Rhubarb can tolerate springtime temperatures in the upper twenties and low thirties. Gardeners should examine their rhubarb and base their decision on plant appearance. Cold damaged rhubarb leaves will shrivel and turn black. Damaged stalks become soft and mushy. Damaged rhubarb stalks should be pulled and discarded. Any new growth, which emerges later in spring, should be safe to eat. Rhubarb plants showing no sign of damage are fine and can be harvested.

Q. When can I start harvesting my newly planted rhubarb?

A. After planting rhubarb, it's usually best to wait 2 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 4-week period in the third year. In the fourth and succeeding years, stalks can be harvested for 8 to 10 weeks.

Q. Can I harvest rhubarb in August?

A. Gardeners should stop harvesting well-established rhubarb plants by mid-June. Continued harvest through the summer months weakens the rhubarb plants and reduces the yield and quality of next year's crop. The rhubarb stalks do become somewhat woody by mid-summer, but they don't become poisonous.

Q. When can I transplant rhubarb?

A. Rhubarb can be transplanted in early spring or early fall (mid-September through early October). Rhubarb does best in fertile, well-drained soils and full sun. The best time to transplant rhubarb is in early spring before growth begins. Carefully dig up the plant with a spade. Large plants may be divided into several sections. Each section should have 2 or 3 buds and a portion of the root system. Transplant each section into the garden with the buds 1 1/2 to 2 inches below the soil surface. Space plants 3 feet apart. Rhubarb also can be successfully transplanted in early fall. Fall planted rhubarb should be mulched with several inches of straw. The mulch provides additional time for the rhubarb plants to get reestablished before the ground freezes.

Q. Why is my rhubarb flowering?

A. Drought, infertile soils, and extreme drought may cause a flower stalk formation. Age may be another factor. Old plants tend to flower more than young ones.

Regardless of the reason, flower stalks should be promptly pulled and discarded. Plants will be less productive if allowed to flower and set seeds.

Flower formation can be discouraged with good cultural practices. Water rhubarb plants once a week during dry weather. Sprinkle 1/2 cup of an all-purpose garden fertilizer, such as 10-10-10, around each plant in early spring. Placement of 2 to 3 inches of well-rotted manure around the plants in early spring is an alternative to a commercial fertilizer.



This article originally appeared in the 5/14/2004 issue.

Year of Publication: 
2004
Issue: 
IC-491(10) -- May 14, 2004