Rhubarb is a perennial vegetable valued for its tart, edible leaf stalks, or petioles, which are commonly used in desserts and preserves. The plant grows from a substantial underground structure called a crown, which is a modified stem and root system. Crown division is the most reliable propagation method for home gardeners, creating an exact genetic clone of the parent plant and ensuring desirable characteristics like stalk color and flavor are maintained. While rhubarb can be grown from seed, this method often results in variable traits and takes significantly longer to reach a harvestable size. Dividing the crown also rejuvenates older plants that have become overcrowded or show reduced vigor over time.
Optimal Timing and Selection of the Crown
The most advantageous time for dividing rhubarb crowns aligns with the plant’s natural dormancy period, which minimizes transplant shock. This window occurs either in late autumn after the foliage has completely died back from the first hard frost, or in very early spring before any new leaf growth begins.
Choosing the right mother plant is crucial for successful propagation and future harvests. The rhubarb plant selected for division should be a minimum of four to five years old, possessing a well-developed, robust crown. Signs that a plant is ready for division include a noticeable decrease in the size or number of stalks, or the production of many thin, spindly petioles instead of thick ones. Always choose a healthy plant that has not shown any signs of disease or pest damage to ensure the vigor of the new divisions.
Step-by-Step Rhubarb Division
The process begins by carefully unearthing the entire root mass of the selected rhubarb plant. Use a garden fork to loosen the soil in a wide circle around the crown, approximately 8 to 12 inches out, before gently levering the entire clump out of the ground. Once the root ball is lifted, brush or rinse off excess soil to clearly expose the crown.
A sharp, clean tool, such as a spade, hori-hori knife, or heavy-duty knife, is needed to cut the crown into separate pieces. Each new division, often called a “set,” must contain at least one to three healthy, visible growth buds, or “eyes,” which appear as reddish-pink points on the crown’s surface.
Ensuring each piece has a sufficient attached root mass is equally important for survival and establishment. Cuts should be made vertically through the crown, aiming to separate sections that include both the buds and a portion of the thick, tuberous root system. Discard any old, woody, or decayed material from the center of the original crown, as this inner section is often less productive. Work efficiently to prevent the exposed root pieces from drying out before they can be replanted.
Successful Transplanting and Initial Care
The newly created rhubarb divisions must be transplanted immediately into a prepared site to ensure their best chance of survival. Rhubarb requires a location with full sun exposure and soil that offers excellent drainage, as the crowns are highly susceptible to rot in waterlogged conditions. Proper soil preparation is necessary since rhubarb is a heavy feeder that will remain in the same spot for years.
The planting area should be amended extensively with well-rotted compost or manure, incorporating organic matter deeply to provide a rich, fertile medium. When planting the divisions, position the crown so that the growth buds are situated just at or slightly below the soil surface, generally no more than one to two inches deep. Planting too deeply can smother the buds, while planting too shallowly can expose them to drying out or frost damage.
After backfilling the hole and tamping the soil gently around the crown, a thorough initial watering is crucial to settle the soil and eliminate any air pockets around the roots. During the entire first growing season, allow the plant to establish its root system fully without the stress of producing harvestable stalks. Refrain from pulling any petioles in this first year; this energy conservation ensures a strong, productive plant for many seasons to come.