Growing rhubarb (Rheum rhabarbarum) is especially suited to climates that are cold enough to grow tulips as perennials (generally Zones 3 to 7). The plants must have a cold-induced period of winter rest, and they also suffer when temperatures rise above 90 degrees Fahrenheit.
In the northern half of North America, rhubarb plants can be phenomenally productive, yielding stalk after stalk for pies, preserves, baked goods and teas. Rhubarb’s sour lemony flavor is due in large part to oxalic acid, which reaches toxic levels in rhubarb leaves. Rhubarb leaves should never be eaten, but are perfectly safe to use as compost or mulch.
Rhubarb varieties vary in stem color, vigor and heat tolerance, but the differences are small.
Two older rhubarb varieties that have stood the test of time, ‘Victoria’ and ‘McDonald,’ produce light green stalks tinged with red. The vigorous disease-resistant plants are good choices for hot summer areas, though they thrive in colder climates, too.
Red stalk color is more pronounced in some rhubarb varieties, including ‘Crimson Red,’ ‘Cawood Delight’ and ‘Starkrimson,’ which can do double duty as edible ornamentals. While red rhubarb is often preferred in markets, red stem color has no bearing on flavor.
If one of your neighbors is growing rhubarb, you may be able to get an excellent locally adapted strain for the asking. Most gardeners with established rhubarb plants have plenty of divisions that can be cut off and shared.
How to Plant Rhubarb
Instead of seeds you should buy rhubarb plants, which won’t cost much because you need only a few. As a general rule, allow only one plant per person in your household unless you have space to spare for these big plants, which mature to 4 to 5 feet across.
Planting rhubarb is best done in spring, around your last frost date. Plant in moist, fertile soil in full sun to partial afternoon shade, but note that rhubarb plants can be moved at other times of the year if soil is kept packed around their roots. Space plants 4 to 5 feet apart, or use them as a focal points dotted around your garden’s boundary. Enrich planting holes generously with compost as well as a standard application of a balanced organic fertilizer when planting rhubarb.
For recommended planting dates for your local climate — and to design your garden beds — try our Vegetable Garden Planner.
Allow a year for transplanted rhubarb to become established in your garden. Mulch to prevent weeds, and provide water during dry spells. In many areas, rhubarb plants deteriorate in midsummer and then make a comeback in fall. Rhubarb plants are killed to the ground by several hard freezes and the roots remain dormant through winter.
In late winter, rake up and compost old mulch and plant debris from your rhubarb patch, and scatter a balanced organic fertilizer over the soil. Top the site off with a thick organic mulch that will deter weeds until the plants leaf out. Pruned tops from large ornamental grasses are seasonally available and useful for this purpose. In late spring, after the plants show vigorous growth, watch for the emergence of huge flower clusters, and cut them off to keep plants from expending energy producing flowers and unwanted seeds.
Harvesting and Storage
A year after planting, harvest two to three rhubarb stalks per plant weekly in late spring by twisting them away from the base. In subsequent seasons, harvest all the stalks you want for six weeks in late spring, and then allow the plants to grow freely.
In many years, rhubarb plants may struggle through summer hot spells to the point of near collapse, and then produce lovely new stems in late summer and fall. Late summer rhubarb is infinitely edible.
After harvesting, top off stalks to remove rhubarb leaves. Cut the rhubarb stalks into uniform length, and store in plastic bags in the refrigerator. Before cooking, remove long strings as you would from celery.
Cooking tip: After cutting the rhubarb stalks into bite-sized pieces, place them in a heat-proof bowl and cover with boiling water, wait one minute, and then drain. This process removes excess astringency so that recipes require a little less sugar. For many more rhubarb cooking tips — plus recipes — go to Eat in Season: Rhubarb.
Established rhubarb plants multiply by division. New offshoots can be dug away and replanted or shared in late spring, when plants are showing vigorous new growth, or in late summer. Plants that have more than three crowns should have the outermost ones removed to preserve plant vigor. Use a sharp spade to sever offshoots without digging up the main crown.
Excess rhubarb plants in need of homes can be temporarily set in a nursery bed, or you can plant them in containers. Soilborne diseases can build up over time, so consider starting a new patch in a fresh site when rhubarb plants are more than 10 years old.
For growing advice for many more garden crops, check out our complete Crops at a Glance Guide.
Contributing editor Barbara Pleasant gardens in southwest Virginia, where she grows vegetables, herbs, fruits, flowers and a few lucky chickens. Contact Barbara by visiting her website or finding her on Google+.