Nicknamed “the pie plant,” rhubarb’s large, juicy stalks have been used for generations to make delicious desserts, pies, and jams. This large-leaved plant is a hearty, cold-weather species that grows best from root cuttings, or “crowns,” instead of seeds. As it needs cooler weather to produce stems, rhubarb will not grow in USDA Zones 9 and higher. Keep in mind that its leaves contain oaxilic acid and are thus toxic both to us and our furry friends; however, with careful disposal of the leaves, rhubarb is a great plant for the beginner gardener.
Ruby rhubarb is a real garden gem with beautiful deep red stalks and lovely green foliage that fades from dark to light towards its tips. If you happen to have a yard with poor soil quality, lack of precipitation, or no yard at all, plant your Ruby in a container: they’re a more compact varietal and are perfectly happy growing in pots or planters. Rhubarb generally takes until the second year to establish, so you’ll have to be patient for your first harvest. We promise the reward will be worth the wait!
Seed Depth: 1/4–1/2″
Space Between Plants: 3–4″ when first planting, thin to 2–4′ between plants after they have reached a height of 4″.
Space Between Rows: 3–4′
Germination Soil Temperature: Minimum 40°F
Days for Germination: 14–21
Sow Indoors: Soak seeds for 2 hours before planting and sow 6–8 weeks before average last frost date.
Sow Outdoors: Not recommended to directly sow seeds outdoors unless you live in climate Zone 7 or higher. Transplant outdoors when plants reach at least 4″.
Vegetative: Growing from a stalk or a piece of crown is the recommended method for growing rhubarb. To propagate from a cutting, split the crown (root piece) of a plant that is at least 5 years of age. Divide the crown, making sure that each piece has at least one bud attached to it. Bury these in the dirt about 2–4″ below surface level in a large hole with plenty of compost.
This plant will grow well in most climate zones but prefers more northerly regions where temperatures get below 40°F in the winter, as this helps promote growth come spring. Rhubarb is cold-hardy and can withstand temperatures as low as -20°F but will wilt and even die in prolonged temperatures above 75–85°F. If you are planting in a region where summers reach higher temps for more than a couple days, we recommend planting your crops in the very early spring as soon as the soil can be worked.
Natural: In cooler regions, rhubarb prefers full sun but will grow in partial shade. If growing in Zone 7 or higher, increase the amount of shade for your plants to avoid wilting.
Artificial: Although this plant prefers full sunlight, it does not require extreme heat, so if starting your plants indoors, a standard fluorescent grow bulb should suffice. Keep bulbs approximately 6″ above seedling tops for up to 10 hours a day. If you notice you are constantly needing to water your seedlings to keep them from wilting, try reducing the amount of time they spend under the lamps.
Soil: Prefers loamy, rich, well-drained soil, especially during transplantation. A pH of 5.5–6.8 will keep plants growing; however, they prefer a soil with a pH of 5.5–6.5.
Soilless: Starts for this plant will grow well in most soilless mixes.
Hydroponics: Although not exceptionally well-suited for hydroponic systems, some folks have had success using these types of systems. If attempting to grow rhubarb hydroponically, we recommend trying an ebb and flow system.
Aeroponics: Can be grown using an aeroponic system; however, it’s not recommended for those who are new to this method of gardening.
Water: Requires moderate to high levels of water. Make sure to keep the soil moist throughout the duration of the growing cycle: the roots might go dormant if they get too dry and the plant will cease to grow. Although rhubarb prefers moist soil, it does not like soggy feet, so ensure that your soil drains well.
Nutrients: Likes nutrients but is not a good competitor, so fertilizer application is highly recommended. If planting in soil that is heavy in sand or clay, it’s particularly important to place cuttings or transplants in a large hole filled with organic compost. Approximately 3–4 weeks after you have planted and every 3–4 weeks thereafter, apply a balanced, organic fertilizer.
Pruning: Following the first season of growth, pull off old stalks to help new ones grow. Do not remove more than 1/4 of the plant at a time. Be sure to cut off flowering seed stalks if they begin to grow.
Mulching: Does well when mulched with organic compost or manure. When the temperatures begin to drop, make sure your plants are surrounded by at least a 3″ layer of compost or other organic material such as grass clippings to ensure the soil will be nourished for the following spring.
Deficiency(s): Yellow leaves or early bolting may indicate a nitrogen deficiency. You can remedy this through the addition of compost, manure, or an organic mulch such as grass clippings.
Rotation: As a perennial, rhubarb may be planted with other perennials but is best left out of other crop rotations.
Companions: Grows well with all members of the brassica family, beans, and alliums, such as garlic and onion.
Harvest: Wait until plants have become well-established, which could occur as late as the second or even third year of growth. You’ll know they’re at this stage when stalks are at least 1″ in diameter and approximately 1′ in height. Rhubarb is harvested by snapping off the stalks at the base. Remove all leafy green parts from them stem and discard.
Storage: Stalks may keep in the fridge for up to 3 weeks but may begin to wilt within a few days.
History: This plant may have only became popular in the US in the late 1700s, but in other parts of the world, rhubarb has been used as a medicine for thousands of years. In fact, the first record of this plant dates back to 2700 BCE where it was used in China as a treatment for stomach ailments.
Preserve: Can be frozen by trimming off the leaves and placing in a sealable plastic bag. Keep in mind that pre-frozen stalks will be limp when defrosted, so don’t use in recipes calling for fresh rhubarb (duh). Stalks can also be dehydrated by placing them on a cookie sheet in the oven on the lowest setting until dried. Store in a container in a dry location. Or try preserving as a tart jam or jelly.
Prepare: Using a sharp knife, cut leaves off of the plant and dispose. Do not eat rhubarb leaves as they are toxic. Using the edge of the knife, lift the outer layer of the stalk and peel off. Once peeled, the stalks may be chopped and turned into a jam, jelly, or pie filling. Although they are a high-acidity food, if preserving, follow any canning instructions carefully to avoid botulism.
Nutritional: Contains moderate levels of vitamin(s) C, K, manganese, calcium, potassium, and some fiber.
Medicinal: Traditionally, this plant was used by the Chinese to lower fevers and as a laxative. Today, some studies suggest that in small doses it can cleanse the digestive tract and colon.
Warnings: The leaves of the rhubarb plant are toxic and should not be consumed.