Extension Viewpoints: Growing rhubarb in your home vegetable garden


By Kathy Kunemund

PREVIEW Columnist

Rhubarb is an easy-growing perennial and can be used to make pie fillings, jellies and jams. It can also be incorporated in breads and cakes. I should also mention that it grows well almost anywhere (hardiness zones 3-8) and requires very little care. If you are unsure of your hardiness zone, view the USDA Plant Hardiness Zone Map at https://planthardiness.ars.usda.gov/PHZMWeb/. Maybe your mother or grandmother has handed down a recipe or two containing rhubarb? 

Seed propagation of rhubarb is not recommended, except in extremely southern areas of the United States. You can, however, purchase rhubarb plants from garden centers, mail-order catalogs or online. Different varieties have varying degrees of sourness and fibrousness.

Varieties can vary in color from green to red. The color will not affect the taste. Rhubarb leaves are toxic and should not be eaten. Only the thick leaf petioles or stalks can be eaten. The stalks contain high levels of oxalic acid. It can tie up calcium in the body and make it unavailable. Small amounts, however, should not pose a nutritional threat. 

The cultivars Canada red, crimson red and Valentine have red stalks, while Victoria, a green-stalked cultivar, are all excellent performers and have great taste.

Rhubarb plants get very large; therefore, each plant will need at least 3 feet around it to grow and flourish. They also require lots of sun. It is best not to plant near trees or large shrubs so they do not compete for sun. Rhubarb performs better in well-drained soil. Organic matter will improve the soil structure. Amending it with manure or compost will improve drainage and should be worked in to approximately 1 foot. Rhubarb depletes a lot of minerals from the soil and should be fertilized once a year.

Plants can be planted outdoors in spring, after the last frost. They must be hardened off for at least one week before planting outside in the garden.

Hardening off is the process of gradually acclimatizing indoor-sown plants to outdoor conditions. The easiest way to do this is to place them outside in a shaded protected spot on warm days and bring them in at night. Each day, increase the amount of sunlight and time outside.

Plants should be consistently watered to the depth of about 1 inch throughout the growing season. Pull weeds as soon as they appear. 

Pests are not usually a problem, except for curculio. It is a large, rusty or dark-colored snouted beetle about 3/4 inches long. It can cause damage by puncturing the stalk. The insect lays eggs in early summer in grassy weeds. The elimination of weeds near the plants will control this pest. If they are found on the plant, I would remove them by hand.

You should not harvest rhubarb the first year of planting. New plants need all of their foliage to build a strong root system; therefore, avoid cutting any stalks from the rhubarb during this time. Stalks can be harvested the second year for one to two weeks and eight to 10 weeks for subsequent years. Start harvesting when they reach about 12-15 inches depending on the cultivar. To harvest, hold the stalk firmly, pull and twist. Trim the leaves and discard immediately (do not consume). Rhubarb can be stored in plastic in your refrigerator for up to four weeks. If you see seed stalks emerge, cut them off at once. Allowing flowers and seeds to set is using up energy and will decrease plant vigor. 

Growing rhubarb is relatively easy and trouble-free. You must wait patiently for it to become established before reaping its benefits. 

Kathy Kunemund has had a lifelong interest in gardening. Her interest propelled her to achieve Master Gardener certification in 2016, and she notes her training provided her with the skills needed to diagnose and solve gardening problems. 

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