Here's How to Grow Rhubarb
By Dr. Mercola
If you’re looking for a hardy, problem-free perennial to add to your garden, consider rhubarb. While you may think of it as a fruit, given the tart-yet-sweet punch it gives to pies and other desserts, rhubarb is actually a vegetable. Given the right soil and sun conditions, you can easily grow rhubarb from crowns or seeds.
For best results, choose a sunny, out-of-the-way corner of your garden that features compost-rich, well-drained soil. Once the plants are established, you can enjoy the red or green celery-like stalks of rhubarb as a springtime treat in jams, pies or smoothies. Avoid the foliage though; it’s poisonous. Here’s all you need to know to grow rhubarb.
What Is Rhubarb?
Rhubarb (Rheum rhabarbarum) is a species of plant in the buckwheat family that is a close relative of garden sorrel. It can be grown as a perennial in U.S. Department of Agriculture hardiness zones 3 to 8. Characterized by its large leaves and tart-tasting stalks, rhubarb loves cool weather. If you live in a cool climate, rhubarb will likely do well because it requires temperatures below 40 degrees F to come out of dormancy. Cold weather also stimulates bud growth.
It is possible to grow rhubarb as an annual in warmer areas. If you do so, keep in mind that too much heat will result in thinner leaves and stalks. This beautiful, ornamental plant grows 2 to 3 feet tall and wide, which is why you need to give it plenty of growing room. It will do best in a back corner of your vegetable garden or another low-traffic area where it can quietly produce year after year.
The red varieties are often preferred for their taste and tenderness, while the green varieties tend to be more productive. If you’ve yet to try rhubarb, the real joy of this hardy perennial is eating its fibrous leaf stalks. Although often mistaken as a fruit, with a composition similar to celery, rhubarb stalks boast a sweet-tart taste that can make your lips pucker.
You can enjoy the look of its leaves but do not eat them. Only rhubarb stalks are edible; the leaves are toxic to animals and humans. They contain a poisonous substance called oxalic acid, which can cause kidney failure if ingested in large amounts. Take care if your rhubarb becomes damaged by frost because The Spruce suggests the stalks may become inedible. “If the stems are not firm and upright, don’t eat them,” they said. “Frost damage can cause the oxalic acid crystals to move into the stalks.”1
The History of Rhubarb
According to the University of Illinois Extension,2 rhubarb is an ancient plant and Chinese rhubarb can be traced back to 2700 B.C. Based on its medicinal properties, it’s believed Chinese doctors employed rhubarb as a body cleansing agent, fever reducer and laxative. NPR3 validates its medicinal use in China and also suggests it has been around for possibly more than 4,000 years.
NPR noted rhubarb was also used in ancient times as a pot cleaner, hair dye and insecticide. Over the years, rhubarb has spread around the world, to Europe, Russia and many other places. It is thought to have arrived in America in the early 1800s.4
Rhubarb Varieties You May Want to Try
While you may be inclined to judge the sweetness of rhubarb according to its color, the two qualities are not so closely related. For example, many mistakenly assume red-stemmed rhubarb is sweeter than other colors, but some green varieties boast a fair amount of sweetness, too. Though there are many to choose from, including pink and speckled varieties, you may want to try one of the following types:5,6
- Cherry Red: A sweet, tender variety with thick, cherry-red stalks that does well in areas with mild winters
- Valentine: Known for its thick red stalks and disease resistance, as well as its vigorous growth
- Victoria: A large, vigorous plant representing the green standard variety of rhubarb; it can produce sweet stems
Tips on Growing Rhubarb
When it comes to growing rhubarb your two biggest decisions are likely to involve location and planting method. Because it is a perennial, you’ll want to select a location where the plant can grow undisturbed year after year. With respect to the planting method, cultivating rhubarb from seed takes more time than growing it from root divisions, which are also known as crowns. Below are some tips from garden experts on how to grow this well-loved plant:7,8,9
Given their perennial nature and the fact they are long-lived, you will want to choose a location for your rhubarb that is in a low-traffic, out-of-the-way area. A back corner of your garden or yard would be ideal.
You can dig a trench or prepare individual holes for each plant that are at least 1.5 feet deep and 3 feet wide. When using crowns, place them every 3 to 4 feet in rows that are spaced about 3 feet apart. Crowded plants will be smaller and less productive. Set each crown about 2 inches below the soil surface and pat the soil gently.
Because you’ll have to wait about two years for your plants to mature when growing rhubarb from seed, you may want to start your plants from root divisions, also called crowns. You can purchase rhubarb crowns at your local garden center or nursery, or online.
Rhubarb will do best in well-drained, slightly acid soil with a pH of 6.0 to 6.8. Because it prefers soil with a lot of rich organic matter, you’ll want to work bonemeal or compost into the area prior to planting. A side dressing of compost in midsummer and fall will ensure healthy, vigorous growth.
Rhubarb likes full sun. If you live in a warm climate, your plants will benefit from light shade, but keep in mind they may produce longer, thinner stems in warm weather.
Water rhubarb crowns immediately after planting and provide enough water to keep the roots from drying out even when the plants are dormant. Mature plants are fairly drought resistant.
Another reason you may prefer to use crowns over seeds is because rhubarb grown from seed can produce plants that are not true to type. For example, if you are interested in a specific rhubarb variety due to its color or stem characteristics, you may not achieve those effects using seeds. On the other hand, if you use crowns you will be more likely to retain the desired attributes of the parent plant.
As soon as your plants sprout, you’ll want to apply a 2- to 3-inch layer of mulch to help keep the soil moist and suppress weeds. You’ll also want to apply mulch in the fall after the foliage dies to protect the plant’s roots from hard freezes during the offseason. As soon as they appear, be sure to remove the flower stalks, which are taller and thicker than leaf stalks. If allowed to mature and bloom, flower stalks will draw nutrients away from the leaf stalks, making them thinner.
How to Maintain Your Rhubarb Plants
Given their hardy nature and assuming they remain unaffected by diseases and pests, your rhubarb plants can remain productive for eight to 15 years.10 Every four or five years, when you notice your rhubarb leaf stalks are thin and the plants have become crowded, it’s time to divide the roots.11,12
Although you can divide in spring or fall, it’s easier in spring because the plant is coming out of dormancy and developing new roots. When the plant begins to sprout, dig up the roots and divide them so each crown has one to three eyes/buds. Then replant them.
Rhubarb Diseases and Pests
While rhubarb diseases are rare, according to Rodale’s Organic Life13 the plant can be vulnerable to Verticillium wilt, a condition that yellows the leaves early in the season or, at later times, can wilt the entire plant. If planted in shady, soggy soil, your plants may suffer from crown rot. With either disease, you’ll want to remove and destroy any infected plants.
You can help your plants resist disease by thinning the stalks regularly to promote good air circulation and removing dead plant material from around the crowns in fall. Fortunately, rhubarb is generally pest free. That said, your plants may occasionally be attacked by cabbage worms or European corn borers. Another likely pest is the rhubarb curculio (or rhubarb weevil),14 which is a distinctive rust-colored beetle with a long snout that you can easily remove by hand.
While this critter does not feed on rhubarb, it bores holes for egg laying into the stalks, roots and crown of not only rhubarb but also other large-stemmed plants. One method to contain this weevil is to remove any nearby wild plants in which it breeds, including dock, sunflower and thistle.
Harvesting Rhubarb: Ready for a Tart Treat?
Below is a summary of the collective wisdom about harvesting rhubarb, with the main goal being to allow the plant to mature fully and position itself for many years of bountiful harvests:15,16
- Similar to asparagus and other garden perennials, you won’t harvest any rhubarb the first year
- During the second year, you can harvest it lightly and only early in the season
- In the third year, your plants will be able to tolerate about a monthlong harvest
- By year four, you can harvest a full eight to 10 weeks
The only exception to the above guidelines relates to warm climates. If you are growing rhubarb as an annual, you can harvest all you want the first year because the plants will last only one year. For perennials, the main harvest season is spring. Weather permitting, you may be able to enjoy smaller harvests throughout the summer or fall, especially in cooler weather. For the tastiest, most tender stalks, remove them as soon as the leaf unfolds.
Limit your cuttings to only one-third of the stalks at a time and stop harvesting altogether whenever the plant is producing skinny stalks. Any decisions you make to allow your rhubarb plants to fully mature prior to harvesting will be more than rewarded. After all, it’s common for one full-sized plant to yield 2 to 6 pounds of tasty stalks each season. As you’d expect, weather plays a role in the harvest: Cool, moist weather increases productivity and warm, dry conditions tend to decrease it.
The best time to harvest rhubarb is in the spring when the leaves are fully developed. Use a knife to cut stalks off at the base or snap them off by twisting them sharply. Take care to avoid injuring underground buds. Due to their toxic nature, remove rhubarb leaves as you go. It is safe to compost the leaves because the oxalic acid crystals will dissipate in the soil long before they would ever be absorbed by other edible plants.17
Enjoying Your Rhubarb
If your palate can tolerate strong, tart flavors, you might enjoy chomping into a stalk of rhubarb right after it’s cut. Most people, however, prefer to blend rhubarb's tangy taste into dessert items such as crumbles, jams, jellies, pies, strudels and tarts.18
Some add it to stuffing, while others feel it brings unique flavor to sauces applied to fish and meat. Other options include adding it to smoothies or pickling the stalks. If you aren’t able to eat all of your harvest fresh, you might consider freezing rhubarb for later use, following these helpful instructions:19
- Wash, trim and cut harvested stalks into 1- or 2-inch pieces
- Blanch the pieces in boiling water for one minute
- Remove the pieces from the boiling water and place in cold water to cool
- Drain well and pack rhubarb pieces tightly in freezer-safe containers, allowing a half-inch of headspace
- Seal, label and freeze; frozen rhubarb will keep for up to one year
Nutrition Facts for Rhubarb
The final reason you should seriously consider growing rhubarb relates to its nutritional profile. Assuming you can resist the temptation to dose it with sugar, rhubarb is a low-calorie, nutrient-rich food. When baking or cooking with rhubarb, try using a natural sweetener such as stevia instead of sugar.
Raw rhubarb contains many health-boosting properties such as polyphenolic flavonoids like beta-carotene, lutein and zeaxanthin, which are known to protect your eyes and skin from the damaging effects of free radicals.20 In addition to being a good source of B vitamins, 1 cup of raw, diced rhubarb contains:21
Calories: 26 grams (g)
Protein: 1.1 g
Carbohydrates: 5.5 g
Fiber: 2.2 g
Sugar: 1.3 g
Calcium: 105 milligrams (mg)
Magnesium: 15 mg
Potassium: 351 mg
Vitamin C: 9.8 mg
Vitamin K: 35.7 micrograms