Find a perfect spot for rhubarb and leave it.
Rhubarb is a perennial vegetable that grows well in most of the United States. Rhubarb is used in pies, tarts, and sauces. Rhubarb should be planted at the end of one side of the garden where it will not be disturbed since it may be productive for five years or more. A single plant will provide enough rhubarb for a family of four. Up to a half-dozen plants if the family really enjoys rhubarb.
When to Plant
Plant or divide rhubarb roots in early spring while the plants are dormant. Planting seeds directly in the garden is not recommended except in extreme southern areas of the United States.
Rhubarb can be grown from seed, but it will add another year or two to getting a full harvest. If using seed, be sure to select high-quality variety as it will be your rhubarb for many years to come. Seed can be started six weeks before the last frost date. Bottom heat and lightly covering the seed with potting mix will aid in germination which may take up to two weeks.
Spacing & Depth
- Plant the roots with the crown bud 2 inches below the surface of the soil.
- Space the roots 36 to 48 inches apart in rows 3 to 4 feet apart.
- Good garden drainage is essential in growing rhubarb.
- Planting on raised beds ensures against rotting of the crown.
- Working plenty of well-rotted manure or compost into the rhubarb bed before planting greatly increases production.
Old roots may be dug and divided to make new plantings.
- Cut the roots into four to eight pieces. Each piece must have at least one strong bud.
- To improve vigor and leaf size, many gardeners divide the old plants and establish a new planting after at least 5 years of full harvest.
- Plantings older than this tend to begin crowding themselves out.
- Dig the roots of the most vigorous, healthy plants to establish a new bed the spring before the old planting is to be discarded.
Cultivate shallowly as often as necessary to remove weeds.
- Apply a complete garden fertilizer before growth begins in the spring and side-dress with a high-nitrogen fertilizer in late June.
- Except in poorly drained sites, organic mulches help moderate soil temperature and moisture. Irrigate during extended dry periods.
- An application of manure or compost is beneficial in late fall or early winter.
- Do not cover the crowns.
Rhubarb curculio, a snout beetle, bores into the stalks, crowns, and roots of rhubarb plants. It also attacks wild dock (Rumex spp.), a group of plants that are prevalent in many areas of the country. Destroy all wild dock growing around the garden. Treat the base of plants with a suggested insecticide. Burn badly infected rhubarb plant parts in July after the beetles have laid their eggs.
Do not harvest rhubarb during the first year of planting. Newly set plants need all their foliage to build a strong root system. Stalks may be harvested for 1 or 2 weeks during the second year and for 8 to 10 weeks (a full harvest season) during the third and subsequent years. Harvest in the fall only when the plants are to be discarded the next season. To harvest, pull the leafstalks from the plant and trim off the leaf blades. The leaf blades contain large amounts of oxalic acid and should not be eaten. To keep the plants healthy, vigorous, and producing well, remove only about one-third of the leaves from a plant at any one time.
If seed stalks and flowers develop during the spring and summer, cut them from the base of the plant as soon as they appear and discard them. Vegetatively propagated, named varieties usually have been selected to produce fewer seed stalks than cheaper, seed-produced plants. The petioles (leafstalks) are of the highest quality (maximum color, flavor, and tenderness) in early spring. They should be crisp and fairly thick. Yield and quality are highest if petioles that have just reached full size are harvested before any coarse fiber can develop.
Selection & Storage
Rhubarb is as hardy as a weed. It is a very beautiful garden plant, with huge extravagant, lush green leaves and pink or red stalks. Rhubarb is an ancient plant as well. Chinese rhubarb has been traced back to 2700 BC. According to folklore, Chinese doctors recommended it for its medicinal qualities as a laxative, to reduce fever and cleanse the body. Rumor has it that rhubarb grown in the United States does not have the same medicinal value as "true rhubarb" or Chinese rhubarb.
Harvesting of rhubarb in Illinois generally begins in mid-June with a second harvest in August. The deeper the red, the more flavorful the stalks are likely to be. Medium-size stalks are generally more tender than large ones, which, may be stringy. For storage, first trim and discard the leaves. The freshly harvested stalks can be kept in the refrigerator, unwashed, and wrapped tightly in plastic, for up to three weeks.
There are several different varieties of rhubarb grown all over the world and used in a variety of cooking preparations. One characteristic consistent with all rhubarb is the toxicity of the leaves and roots. The rhubarb leaves contain high amounts of oxalic acid, a toxic and potentially deadly poison. Only the stems are edible, although the first crops were grown for the round pouch of unopened flowers, which was cooked as a delicacy (in northern Asia it is still raised for this purpose). The stems still do contain some oxalic acid. Those with gout, kidney disorders, and rheumatoid arthritis may want to consult with their physicians about consuming these foods.
Questions & Answers
Q. A severe freeze has damaged my rhubarb. Can I safely eat the leafstalks?
A. No. The leafstalks will be of poor texture and flavor and oxalic acid may have migrated from the leaf blades.
Q. Why do my rhubarb plants send up seed stalks and produce small leaves and leafstalks? The petioles are not as large as they have been in previous years.
A. These conditions may result from excessive crowding, old plants, or low soil fertility. Allow more space between rhubarb plants, divide parent plants, and fertilize regularly. Some seed-propagated plants produce small foliage and many seed stalks even under the best conditions. Buy only named, vegetatively propagated varieties; or get divisions from another gardener who has a high-quality planting.
Preparing Rhubarb for Exhibition
Former Illinois Extension Horticulturist Jim Schmidt demonstrates how to properly prepare rhubarb for exhibition, including whether rhubarb should be pulled or cut.