I love rhubarb as a food. Its tartness balances the sweetness of pie, cake, syrup, muffins, juice and sauce. I also love rhubarb as a landscape plant with its big, coarse leaves, bright red stalks (technically the leaf petioles), and its sheer presence as a perennial, edible crop. My mom grew rhubarb as did my aunts. Neighbors share rhubarb and you can find it at farmers’ markets, co-ops, grocery stores, and fruit and vegetable stands.
CAUTION: While rhubarb stalks are edible and delicious, the leaves are toxic. They contain oxalic acid and can make you very ill when eaten. Cut them from the stalks and compost them.
Maximize your rhubarb’s potential
Rhubarb is a perennial plant that is cold-hardy to zone 4 and definitely worth trying in zone 3. In order to grow to its full potential and supply thick, juicy stalks for all those good foods, rhubarb is serious about needing the basics: full sun, well-drained soil, and room to spread out its large leaves. It is also a “heavy feeder.” According to Growing rhubarb in home gardens, rhubarb should be supplemented annually with a balanced fertilizer or rich compost or both.
That said, a soil test is always a good first step before adding fertilizer and compost or manure to soil. Minnesota soils are naturally high in phosphorus (P) so you don't need to add more. I recently submitted soil samples for a few garden beds in my yard and my P was “very high” as was the organic matter (OM) and my potassium levels (K). The soil testing lab recommended only nitrogen (N) for my garden beds. A couple easy options for me are blood meal (13% N, and only 2% P and 1% K, or synthetic urea which is 46% N and contains no P or K.
Plant rhubarb in spring
Gardeners often divide and share rhubarb plants. But, with the danger of spreading jumping worms, an invasive species, purchasing plants is a better option. And while rhubarb can be started from seed, plants are generally a faster route to eating. Some cultivars recommended by our colleagues at University of Wisconsin Extension are ‘Canada Red’, ‘Cherry Red’, ‘Crimson Red’, ‘MacDonald’, ‘Valentine’ and ‘Victoria’. New plants should be allowed to grow unharvested for the first season and harvested the second. Plants grown from seed should not be harvested until Year 3.
Provide your rhubarb with one inch of water per week (remember to consider rainfall too). Rhubarb doesn’t have much in the way of pests: leaf spots don’t affect harvest, and keeping weeds under control will prevent pests such as rhubarb curculio and stalk borers from invading plants.
Don’t underestimate the size of a mature rhubarb plant. A single rhubarb plant can occupy 3 square feet of ground.
Full sun — a minimum of 6 hours of direct sunlight — is also necessary as is well-drained, loamy soil. Soil that is too wet and doesn’t drain well can result in root rot. On the flip side, sandy soil will not hold enough moisture for the plant to take up nutrients from the soil.
Harvest until the end of June
Harvest rhubarb in spring as the leaves and stalks become large enough. Grasp, twist and pull the stalks from the base of the plant, being careful not to pull the plant from the soil. Pick rhubarb until the end of June and allow it to just grow the rest of the season. Throughout the summer, the large green leaves will photosynthesize and send energy down into the roots for next year’s crop.