One of spring’s garden harbingers, rhubarb stems burst through soil early in the growing season. The tart, colorful stems grace pies and jams with tangy flavor that is typically tamed with sugar or teamed with sweet strawberries.
A true perennial, rhubarb adds sculptural beauty to the garden with its blocky stems and large leaves. While leaves offer textural beauty, they’re not part of the harvest package. Rhubarb leaves contain high concentrations of oxalic acid and shouldn’t be eaten. When harvesting stems, remove leaves and add them to the compost pile.
Rhubarb grows best in zones where the ground freezes in winter. Plants require an extended chilling period with temperatures below 40 degrees to produce a crop of stems. As a result, rhubarb is commonplace in gardens throughout the coldest sections of the country, although it can be grown as far south as Zone 7.
A true perennial, rhubarb plants can yield harvests 5 to 8 years or longer. Once plants are established, they don’t transplant easily, so choose your planting site carefully. Rhubarb thrives in full sun but will yield to light shade. Select a location that gives plants ample room; individual rhubarb plants can measure 4 to 5 feet across.
Plant crowns in spring as soon as soil is workable. Tuck plants into slightly acidic soil rich in organic matter. Rhubarb crowns require shallow planting, but because plants are such heavy feeders, you should dig planting holes at least a foot deep. Fill the hole with a mixture of well-rotted manure or compost blended with the soil you removed. Bring that nearly level with surrounding soil, so that your plant crowns are 2 to 4 inches deep. If your soil is heavy clay, plant rhubarb in raised beds.
Water newly planted crowns, and keep soil moist throughout the growing season. As summer heat arrives, mulch plants with a 2-inch-thick layer of organic mulch, such as compost, straw, or shredded bark. Replenish mulch throughout the growing season as needed to maintain 2-inch thickness.
Remove flower stalks as soon as they emerge. Plants that flower make fewer stems the following year. You can extend the stem-harvesting season of established plants by making sure that they have adequate moisture and by removing flower stalks.
In fall, when stems die back, remove all plant debris. Mulch plants after the ground freezes, covering crowns with 2 to 4 inches of compost or leaves. In regions where frost kills plants, applying manure to plants in fall provides effective fertilizer. Otherwise, fertilize established plants in spring with an extended-release fertilizer such as 19-19-19 or organic fertilizer. Mulching plants with well-rotted compost adds nitrogen to the soil throughout the growing season.
Established plants need to be divided every 5 to 10 years. You’ll know it’s time to divide when stems are crowded and thin. Divide when plants are dormant, in early spring or fall. Dig and lift clumps, cutting roots into pieces about 2 inches across. Take care not to damage the buds on the top of each root section. Replant the best sections.
Few problems plague rhubarb. Crown rot settles in when soil drainage is poor. This disease damages terminal buds, which results in spindly, weak stems. The cure is to dig out and burn infected plants. Don’t replant rhubarb in areas where crown rot has damaged plants before.
Leaf spots can attack the plant, with the worst being red leaf, or Ramularia, which can ruin the stems. Cut away old foliage in fall to help prevent leaf spot, whose spores overwinter in the debris.
Rhubarb curculio occasionally attacks plants. Insects puncture leaf stalks from late spring to early summer as they feed and lay eggs. Damaged stems ooze sap and may begin to decay.
Forget harvesting the year that you add rhubarb to the garden. In the second year after planting, harvest lightly, removing only a few stalks from each plant. From the third year on, harvest stems freely. To ensure continued production, take care not to remove more than one-third to one-half the stalks from any one plant during any one harvest.
To harvest, choose stems that are 12 to 18 inches long and reddish in color. Grasp the stalk near the base and pull it upwards, twisting the stem as you pull. You can also use a sharp knife to slice stems from the plant. Cut as close to the crown as possible without damaging it. After harvesting, remove the leafy portion and the base of the stem, leaving only the colored stalk.
Early spring stems offer the most flavor and tenderness; they’re ideal for pies. Stems harvested later in the season are often pithy. Reserve these stems for stewing, sauces, or jams.
Stop harvesting as stems get shorter and thinner. At this point, plants are storing up energy for next year’s harvest. Mature plants typically provide an 8- to 10-week harvest. In general, expect 2 to 3 pounds of stalks per mature plant per season.
For the best quality in cooking or freezing, use freshly harvested stalks. If that is not possible, keep cut stems up to 1 week in the refrigerator, although crispness diminishes with storage. You can refresh crispness by standing stored stems in water before using; however, the flavor will be slightly diluted. You can also chop stems and freeze the pieces in a plastic freezer bag for much later use.
I planted rhubarb this spring. When can I start picking?
White stalks are rising out of the center of my rhubarb plants. What are they?
How do I know when rhubarb is ready to pick?
How do I harvest rhubarb?
Can I harvest stems from a mature rhubarb clump all summer?
My rhubarb was growing fine, then stalks began to fall over and rot. What is happening?
My rhubarb patch is so healthy that plants are crowding one another. Can I divide them, and if so, when?