Rhubarb’s unique flavor makes it a favorite ingredient in pies and desserts. It is high in vitamins A and C, thiamin, riboflavin, niacin, potassium, phosphorous, and dietary fiber. Although it provides all these healthy nutrients, rhubarb comes with an important caveat: the leaves contain oxalates which make them poisonous. Therefore, rhubarb should not be eaten raw. Only use the stalks in cooking or baking.
Rhubarb is a cool season perennial that is relatively resistant to pests. It grows from fleshy roots (rhizomes), producing large, thick succulent petioles (stalks) that are edible. Rhubarb stalks emerge from the eyes in early spring. A producing plant grows up to two feet tall and wide, with the stalks getting up to 18 inches long and one to two inches wide. Two varieties that do well in Marin are the Crimson Cherry (red stalks) and Victoria (green stalks with red shading).
Best conditions for growing rhubarb
Rhubarb grows best where the average temperature is less than 75 degrees but requires a minimum temperature of 40 degrees to break dormancy. It needs fertile, well-drained soil high in organic matter. It is advisable to remove all weeds in the area where you plan to place the roots, as it does not tolerate weed growth. After the first year, when the plant is producing leaf stalks, you can pull some of them and place the leaves around the base of the plant. The oxalic acid in the leaves stops weeds from growing.
Rhubarb is tolerant of soil acidity but grows best in slightly to moderate acid soil with a pH of 6.0 to 6.8. Do not mix fresh manure into the soil, as it will burn the plant.
Plant rhubarb rhizomes in winter or early spring (December through March) and as soon as possible after purchase or division to prevent the roots from drying out. If the ground is extremely wet, plant the rhizomes in gallon containers until the soil dries out and is easily worked. Each rhizome should have at least one good, strong bud. Make sure to plant the rhizomes in the ground before the buds break and begin producing new leaves and petioles.
Space roots 24 to 48 inches apart for good air circulation. Plants placed closer than 36 inches apart will diminish the crop and increase the likelihood of spreading disease. Plant the roots with the crown bud two inches below the surface of the soil in good draining soil. Add compost, peat moss, and 1/4 cup of 5-10-10 fertilizer into the top ten inches of the hole, and water thoroughly.
Rhubarb grows vigorously into early summer and becomes dormant until the winter rainy season. Remove any flower stalks as soon as they appear.
Do not pick the stalks during the first year of growth as they are nourishing the roots for the next year’s growth. Lightly pick the petioles in the second year if the plant exhibits vigorous growth. Stalk color is best when the plant is two to three years old.
Harvest rhubarb in early spring to early summer, depending on local weather conditions. When harvesting, pull or cut the petioles from the crown. Do not over harvest; a certain amount of foliage needs to be left on the plant for the development of the present crop as well as the following year’s crop. Do not use stalks that have been frozen or that are limp; only pick upright and firm stalks.
Stalks should be cooled rapidly after picking to prevent wilting at 32°F (0°C) and 95 to 100 percent relative humidity. Fresh rhubarb stalks in good condition can be stored for two to four weeks.
Plants can be protected in the winter from frost with a mulch of leaves or compost at the depth of two or three inches. Feed the rhubarb with 10-10-10 fertilizer each spring along with a compost mulch. It is advisable to divide the roots every five to seven years to increase the vigor of the plant. When dividing, make certain to keep three to five buds in each crown.
Rhubarb is delicious in breads, cookies, pies, cobblers, jams, and sauces or meat condiments. Its acidic taste is due to oxalic acid; adding sugar softens the acidic flavor. You can freeze rhubarb and use it for cooking or baking later.
There is no better time to enjoy a piece of rhubarb pie than on June 9th, National Strawberry Rhubarb Pie Day. Enjoy this vegetable year round.
Original article by Sonoma UC Master Gardener Joe Michalek
Edited for the Leaflet by Lisa MacCubbin