Rhubarb is a unique herbaceous perennial, botanically classified as a vegetable yet often prepared culinarily like a fruit. Its long-term productivity, which can span a decade or more, is directly tied to the strength and structure of its subterranean system. Unlike annual plants, rhubarb’s survival and yearly yield are entirely powered by its robust, permanent root system. The ability of the plant to return each spring with vigor is a testament to the specialized anatomy and function of its crown and roots.
Anatomy of the Rhubarb Crown and Roots
The physical structure beneath the soil consists of two main specialized components: the crown and the roots. The crown is the central, thickened underground stem, or rhizome, that serves as the plant’s hub of activity. This dense cylinder forms and stores the buds that develop into the edible leaf stalks.
These buds are the growing points for the plant’s above-ground portion, emerging from the crown’s surface each spring. Extending outward and downward from the crown are the fleshy storage roots, a dense network of fibrous and woody rhizomes. These roots anchor the large plant and absorb water and nutrients from the surrounding soil.
The crown and roots work together in a continuous cycle of growth and renewal. The crown is the source of new growth, while the roots provide structural support and store the energy reserves needed to fuel that growth. This dual-purpose underground system allows the plant to survive harsh winter conditions and quickly resume production in the spring.
The Role of the Root System in Energy Storage and Sustainability
The rhubarb root system functions as a specialized storage organ, designed to sustain the plant through its annual dormancy cycle. The fleshy rhizomes and roots accumulate large amounts of carbohydrates, primarily starches, during the late summer and fall. This stored energy is the biological reserve the plant draws upon to initiate rapid, early-spring growth before the leaves are large enough to photosynthesize effectively.
The plant requires a period of cold temperatures, or chilling hours, to properly break dormancy and stimulate the formation of new leaf buds. This cold exposure ensures the stored carbohydrates are correctly mobilized for the following season’s growth. The sustained productivity of the rhubarb plant is directly tied to the replenishment of these root reserves each year.
This energy storage mechanism dictates responsible harvesting practices. Excessive harvesting, particularly later in the growing season, can severely deplete the carbohydrate reserves stored in the roots. If the plant is forced to expend more energy than it can replace, the crown reserves are diminished, leading to thinner stalks and reduced vigor in subsequent years. Gardeners must cease harvesting in mid-to-late summer to allow the plant sufficient time to transfer and store energy back into its root system before winter dormancy begins.
Propagating and Maintaining the Rhubarb Root System
The perennial nature of rhubarb allows for its propagation through the physical separation of the crown, a process known as division. This technique is typically performed when the plant is dormant, either in late fall or early spring. Division is generally recommended every five to ten years to maintain the plant’s vigor and prevent overcrowding.
To create new plants, the entire root mass is carefully lifted from the soil and sliced into sections. Each piece must retain at least one large root section and one or two healthy buds.
Proper planting depth is a determining factor in the success of a new or divided crown. The crown should be positioned so the buds are just below the soil surface, typically covered with only one or two inches of soil. Planting too deeply can delay production or cause the crown to rot, while planting too shallowly can expose the buds to damage.
Long-term maintenance of the root system relies on providing rich, well-draining soil with regular amendments. Rhubarb is a heavy feeder due to the energy demands of its large, leafy canopy and extensive storage roots. Annual application of well-rotted manure or compost around the base of the plant feeds the roots and helps retain the moisture they need to thrive.