University of California
UC Master Gardener Program of Sonoma County
Somewhat surprisingly, rhubarb is a member of the buckwheat (Polygonaceae) family. It traveled west from central Asia with Marco Polo and was brought to North America by Benjamin Franklin. Its unique tangy flavor is sometimes enjoyed sweetened as a relish but more often in pies and desserts.
- Rhubarb’s perennial, fleshy rhizomes and thick, succulent stalks grow best in cool microclimates where the average summer temperature is less than 75 degrees.
- Plants enter dormancy in cold winters. In mild microclimates, they do not die back completely.
- Rhubarb is harvested in spring, possibly late winter if growth resumes early, and continues for about 2 months. Summer growth nourishes rhizomes for the next year’s harvest.
- Rhubarb needs fertile, well-drained soil high in organic matter. Some shade is tolerated.
- Clumps can grow up to 2 ft. high and 3 ft. wide with the stalks 18 in. long and 1-2 in. wide.
- Only stalks are harvested with no trace of foliage.
- Leaves, rhizomes, and roots are poisonous.
- Stalks must be pulled, not cut, to avoid leaving a stub that will rot.
- Rhubarb is generally resistant to pests.
Planting and Growing
- Prepare a fast-draining planting area by mixing in compost and other organic matter such as well-aged manure with ¼ cup of 5-10-10 fertilizer into the top 10 in. and water thoroughly.
- Divide existing mature plants or purchase bare root divisions December-March. Plant immediately or pot up bare roots if soil is too wet; plant in the ground before buds break and begin producing new leaves and stalks.
- Bury roots with the crown bud 2 in. below the soil surface. Space roots 24-28 in. apart. Planted closer than 36 in. diminishes the crop. Expect growth to emerge from the eyes in early spring.
- Feed rhubarb with 1 cup of a balanced fertilizer such as 10-10-10 each spring along with a compost mulch. Do not use fresh manure; it will burn the plants.
- Remove flower stalks as soon as they are observed. They grow in response to low fertility.
- Keep beds weed free. Place leaves from harvested stalks around the base of the plant. Oxalic acid in leaves prevents weeds from getting established.
- Do not pick stems the first year plants are in the ground. Their leaves are nourishing roots for the next year’s growth.
- Pull stalks from the crown to harvest one light picking the second year if the plant is vigorous.
- Frosted stalks in early spring can be picked and eaten as long as they are upright and firm.
- Plants can be protected in the winter with a mulch of leaves or compost 2-3 in. deep.
- Divide clumps every 5-7 years to increase their vigor. When dividing, make certain to keep 3-5 buds in each crown.
- Sonoma County Master Gardener Vegetable Planting Summary