By Joe Michalek, Sonoma County Master Gardener
Rhubarb is the common name for Rheum rhabarbarum, a member of the buckwheat family. It originally grew wild in central Asia going back to 2700 B.C. and was brought west by Marco Polo. It was introduced into Britain in the sixteenth century and, subsequently, Benjamin Franklin brought it to North America in the eighteenth century. Its unique flavor makes it a favorite ingredient in pies and desserts. It also is high in vitamins A and C, thiamin, riboflavin, niacin, potassium, phosphorous and dietary fiber.
Rhubarb is a cool season perennial that is relatively resistant to pests. It grows from fleshy rhizomes producing large, thick succulent petioles (stalks) that are use as food. Rhubarb stalks emerge from the eyes in early spring. The producing plant can grow up to two feet high and wide with the stalks getting up to 18 inches long and one to two inches wide. The Sonoma County Master Gardener Vegetable Planting Summary recommends that rhubarb be planted December through March. Two varieties that do well in our area are the Crimson Cherry (red-stalked) and Victoria (speckle-stalked).
Rhubarb grows best where the average temperature is less than 75° but requires a minimum temperature of 40° to break dormancy. It needs fertile, well-drained soil which is high in organic matter. It does not tolerate a weedy patch. So, it is advisable to kill all of the weeds in the area where you plan to place the roots. After the first year, when the plant is producing petioles, you can pull some of them and place the leaves around the base of the plant. The oxalic acid in the leaves precludes the weeds from getting established.
Rhubarb is tolerant of soil acidity but grows best in slightly to moderate acid soil with a ph of 6.0 to 6.8. Fresh manure should not be used as it will burn the plants. Roots (rhizomes) should be planted as soon as possible after purchase or division from a friend. If the ground is too wet when purchased and you cannot heal them in, they should be potted up in gallon containers until the soil can be worked. In any case, plant them the ground before the buds break and begin producing new leaves and petioles.
Space roots from 24 to 48 inches apart for good air circulation. In a small garden, plants closer than 36 inches apart will diminish the crop and increase the likelihood of spreading disease. Plant the roots with the crown bud 2 inches below the surface of the soil in good draining soil. It is advisable to add compost, peat moss and 1/4 cup of 5-10-10 into the top 10 inches of the hole and water thoroughly. Remove flower stalks as soon as they are observed. When harvesting, one can either pull or cut the petioles from the crown. During the first year of growth the stems should not be picked as they are nourishing the roots for the next year’s growth. The second year there can be one light picking if the plant exhibits vigorous growth. Frosted stalks can still be picked and eaten just as long as they are upright and firm. Plants can be protected in the winter with a mulch of leaves or compost at the depth of 2 or 3 inches. Feed the rhubarb with a cup of 10-10-10 fertilizer each spring along with a compost mulch. It is advisable to divide the roots every 5 to 7 years to increase the vigor of the plant. When dividing, make certain to keep 3 to 5 buds in each crown.
Only the stalk is eaten. Do NOT eat the green leaves which are poisonous. Rhubarb is delicious in breads, cookies, pies, cobblers, jams, and sauces or condiments for meat. It can be frozen to be made into any delightful item you desire later. Combining a fruit and a vegetable into a pie makes this a great dessert in the summer. There is no better time to enjoy a piece of this delectable pie than on June 9th, National Strawberry Rhubarb Pie Day. Enjoy this vegetable year round.