Rhubarb (Rheum rhabarbarum) is a vegetable that’s usually prepared and eaten like a fruit, turned into pies, jams, jellies, and more. This cool-season crop, which is perennial in many areas, is grown for its fibrous leaf stalks that can make a wonderful tart treat. In addition, rhubarb can be a beautiful ornamental plant with its large, textured leaves and chunky stems. Rhubarb plants are generally hardy and long-lived, with some varieties growing for 20 years or longer.
Rhubarb has a fast growth rate. Plant in the early spring, but don’t start harvesting until the second growing season. Also, note that rhubarb leaves and roots are toxic both to people and pets.
|Botanical Name||Rheum rhabarbarum or Rheum × hybridum|
|Plant Type||Vegetable, perennial|
|Size||2–3 ft. tall; 3–4 ft. wide|
|Sun Exposure||Full sun, partial sun|
|Soil Type||Moist, well-drained|
|Soil pH||Acidic, neutral (6.0–7.0)|
|Bloom Time||Spring, summer|
|Hardiness Zones||3–8 (USDA)|
|Toxicity||Toxic to people, toxic to pets|
How to Plant Rhubarb
When to Plant
Rhubarb should be planted in cool early spring temperatures once the ground has thawed and becomes workable.
Selecting a Planting Site
Select a sunny spot in the garden with good soil drainage. Because rhubarb can live for many years, aim to pick a spot where it can grow undisturbed. Make sure no nearby tree or shrub will eventually grow too tall and shade it out. In addition, rhubarb doesn't like competition from weeds, so adding a 2-inch layer of mulch will help to suppress them. Rhubarb also can be grown in containers.
Spacing, Depth, and Support
Rhubarb is usually grown from purchased crowns (root divisions), rather than from seed, to speed up the harvest. Plant crowns around 4 inches deep and 4 to 6 feet apart. If placed too close together, the rhubarb will be smaller and less productive. You can plant in a long trench, much like asparagus, or dig individual holes. Rhubarb plants do not require a support structure.
Rhubarb tends to produce best when planted in full sun, meaning at least six hours of direct sunlight on most days. However, plants in the warmer growing zones usually benefit from some afternoon shade, especially during the hottest months of the year. Too much shade, however, can result in thin stems.
Rhubarb prefers a slightly acidic to neutral soil pH. In addition, it likes soil that's high in organic matter, which helps to support its growth. The soil should be moist but well-draining. If you have heavy soil, such as clay, consider planting your rhubarb in raised garden beds to provide the appropriate growing environment.
Rhubarb likes consistent moisture. While mature plants can be somewhat tolerant to drought, rhubarb in its first two years of growing needs regular watering. However, don't overwater rhubarb, as the crowns can rot in wet soil. A good rule is to water the plant when the top inch of soil dries out.
Temperature and Humidity
Rhubarb likes climates in which the average temperature is below 40 degrees Fahrenheit in the winter and below 75 degrees Fahrenheit in the summer. It can be grown as an annual in warmer areas; however, too much heat can cause it to have thin stalks and leaves. Dry climates will make it difficult to maintain the level of moisture rhubarb craves, though a layer of mulch to conserve soil moisture can help.
Rhubarb needs lots of organic matter, such as compost, in the soil to grow well. Don’t use any chemical fertilizer on a young rhubarb plant, as the nitrates can kill it. You can add an organic fertilizer around your plant at the start of its second growing season, but make sure it’s safe if you intend to eat your rhubarb.
Rhubarb is a self-pollinating plant.
Types of Rhubarb
There are several types of rhubarb, each with certain attributes that make it desirable to grow. Here are a few common varieties:
- 'Victoria': This is a popular rhubarb variety for cooking, thanks to its mild and tender stalks.
- 'Valentine': This variety is hardy against climate fluctuations and diseases.
- 'Crimson Cherry': This variety is known for its sweetness.
- 'Canada Red': This plant does well in colder climates and contains more sugar than many other rhubarb varieties.
Rhubarb vs. Red Chard
Red chard sometimes can be mistaken for the bright red stalks of rhubarb. However, chard is a vegetable while rhubarb is a fruit. And chard leaves are edible while rhubarb leaves are not.
Don't harvest any rhubarb in your plant's first growing season to allow it to become established. You can take a small harvest in the second growing season. During the third season, you can harvest freely, but never harvest more than a third to half of the plant at one time. However, if you're growing rhubarb in a warm climate as an annual, you can harvest all you want the first year because the plant likely won't survive a second year.
The main harvest season is the spring, though smaller harvests might continue throughout the summer. Stalks that are red and around 12 to 18 inches long are ready for harvesting. To harvest, cut the stalks at the soil line. Then, remove the leaves. Cook or freeze newly harvested stalks right away, or keep them in the refrigerator for up to a week. The stalks harvested in the spring usually have the best taste and tenderness for pies. Later-season stalks can be tough and often best stewed in jams and sauces.
How to Grow Rhubarb in Pots
If you have heavy soil or not enough space for rhubarb in the garden, it can be grown in a container. Rhubarb has a large root system and thus needs a large pot in which to grow. Choose one that’s at least 12 inches in diameter, and make sure it has drainage holes. An unglazed clay container is ideal, as it will allow excess soil moisture to escape through its walls.
Remove any flower stalks, which are taller than leaf stalks, as soon as they appear. If rhubarb is allowed to mature and flower, the leaf stalks will be thinner.
Rhubarb is best propagated by division. You can do this in the early spring or fall, though it’s easier in spring when the plant is coming out of dormancy and growing new roots. Dividing rhubarb plants roughly every five years is ideal to keep them healthy and vigorous. You’ll know it’s time to divide when the plant starts to produce thin stalks. Here’s how:
- Dig up the plant, keeping its roots as intact as possible.
- Gently split the crown into pieces around 2 inches across with roots attached to each section.
- Replant the sections at least 4 feet apart (or in entirely different locations). Water well.
How to Grow Rhubarb From Seed
Rhubarb is not commonly grown from seed, as it can take several years to get a good harvest and sometimes seeds can be difficult to find. If you wish to start plants from seed, fill a tray with moistened seed-starting mix. Soak the seeds in warm water for about an hour before planting, and then plant them about an inch deep. Cover the tray with plastic wrap to retain moisture, and place it in bright, indirect light. Ensure that the soil remains moist but not soggy. Seedlings should appear in one to two weeks.
Potting and Repotting Rhubarb
A well-draining potting mix made for vegetables is typically good for rhubarb. Plant the crown around 4 inches deep in the pot just like you would in the ground, and water after planting to evenly moisten the soil. Plan to repot once you see roots growing out the bottom of the container and up above the soil line. You’ll likely have to do this roughly every three years, depending on your container size. You can either divide the plant into separate containers or repot the whole plant into a larger container. Wait one growing season before harvesting from a repotted rhubarb plant.
Rhubarb stems will die back in the fall. At that time, cut the depreciated foliage to the ground. Then, cover the plants with 2 to 4 inches of mulch once the ground freezes to protect the roots and keep them from drying out over the winter.
Common Pests and Plant Diseases
Rhubarb can be susceptible to crown rot, especially in poorly drained wet soils. Foliar leaf spots also can occur, but while disfiguring, this does not usually hinder harvest of the stalks.
Moreover, stalk borers, beetles, and rhubarb curculio can infest rhubarb. Either organic or chemical pesticides will generally control these, though you should follow label directions for using these compounds with edible plants. Keep the ground around the plants free of debris to remove breeding areas.
Is rhubarb easy to grow?
Rhubarb is typically an easy and vigorous grower with the right light and soil conditions.
How long does it take to grow rhubarb?
Rhubarb crowns grow quickly but shouldn't be harvested in their first growing season.
Does rhubarb come back every year?
Rhubarb is a perennial in cooler climates, and most varieties will live for many years.