Rhubarb is a hardy perennial vegetable appreciated for its tart stalks. As a long-lived plant, it requires minimal yearly care, but the central root structure, known as the crown, eventually benefits from division. Division is a necessary maintenance task that rejuvenates the existing patch, ensuring the rhubarb continues to produce a strong, healthy harvest year after year. Understanding the optimal timing and technique for this process prevents stress to the plant and maximizes the chance of successful establishment.
Recognizing When Rhubarb Needs Division
A mature rhubarb plant signals its need for division through noticeable changes in its appearance and production. A reduction in the quality and quantity of the harvest is common, with the plant yielding thin, spindly stalks instead of thick, robust ones. This indicates that the crown is becoming overcrowded and its resources are spread too thin. The crown itself may show signs of age, becoming dense, woody, and hard in the center, which restricts new growth and nutrient uptake. This overcrowding can also lead to poor air circulation, increasing the likelihood of rot and disease. Rhubarb should be divided every five to ten years to maintain peak productivity and vigor.
The Best Time of Year for Dividing Rhubarb
The best time to divide rhubarb is during its dormant season, when the plant has naturally shut down its above-ground growth and is conserving energy in its root system. There are two main windows for this task: early spring or late fall.
Dividing in early spring is preferred by many gardeners, as it is done just as the ground thaws and before the first tender shoots emerge, making the dormant buds easy to identify. This timing allows the divisions to immediately begin establishing roots as the soil temperature rises. Conversely, late fall division is done after the foliage has died back completely, usually following the first hard frost. Fall division gives the root sections a full winter to settle into the soil before the demands of spring growth begin. This ensures the stored energy in the root mass, or rhizome, is available to support the new plant segments.
Preparing and Separating the Crown
The physical process begins by carefully digging up the entire crown, using a spade to loosen the soil in a wide circle around the plant to preserve as much of the root mass as possible. Once the crown is lifted, excess soil should be gently removed to expose the woody root system and the reddish, pointed buds, known as “eyes.”
The crown must then be separated into smaller sections, which can be accomplished using a sharp, clean spade, a large knife, or even an axe for very old, tough crowns. Each resulting division must contain at least one healthy bud, although segments with two or three buds and a substantial portion of the root mass are preferred for a quicker start. Discard any woody, decayed, or soft, mushy material from the center of the old crown, as this helps prevent the spread of potential root diseases.
Establishing New Rhubarb Plants
After separation, the new rhubarb divisions should be replanted immediately to prevent the roots from drying out. The planting site should be prepared by amending the soil with a generous amount of organic matter, such as compost or well-rotted manure, to ensure rich, well-draining conditions.
The sections are planted so that the buds sit just slightly below the soil surface, about one to two inches deep, and should be spaced at least three feet apart to allow for mature growth. Immediately after planting, the new divisions require a thorough watering to settle the soil and eliminate air pockets around the roots. For the first year after division, abstain from harvesting any stalks, allowing the plant to dedicate its full energy to developing a strong, robust root system.