Rhubarb is a perennial vegetable, widely recognized for its tart, edible leaf stalks. Often mistaken for a fruit due to its culinary uses in pies and desserts, this resilient plant can remain productive for a decade or more. Understanding its distinct growth stages is key to successful cultivation and ensuring a consistent harvest of its flavorful stems.
Rhubarb’s Perennial Life Cycle
Rhubarb is a perennial plant with a cyclical growth pattern, returning year after year from its established root system. Each winter, the plant enters a dormant phase, shedding its foliage and conserving energy within its underground crown. This period of rest is essential for its long-term vigor and subsequent spring growth. As temperatures rise, the plant emerges from dormancy, beginning a new cycle of growth, development, and preparation for the next winter.
Key Rhubarb Growth Stages
Dormancy
During the colder months, rhubarb enters dormancy. All above-ground foliage dies back, and the plant’s energy is stored within its fleshy, reddish-brown rhizomes and crown, which remain alive underground. Rhubarb is a cold-hardy plant, requiring winter temperatures below 40°F (4°C) to break dormancy and stimulate vigorous spring growth.
Spring Emergence
As soil and air temperatures begin to warm, the first signs of new growth become visible. Red-tinged shoots emerge from the soil, unfurling tightly folded leaves. These initial stalks are often more slender and may have a distinct reddish hue before expanding into larger leaves and thicker petioles.
Rapid Stalk Development
Following emergence, rhubarb enters a period of vigorous growth. The stalks lengthen and thicken, reaching up to 18 inches long and 1-2 inches in diameter, while the large, heart-shaped leaves expand considerably. During this phase, the plant focuses its energy on developing robust foliage and storing carbohydrates in its crown. This rapid growth is especially pronounced in cooler spring temperatures, ideally below 75°F (24°C).
Flowering and Seed Production
Mature rhubarb plants may produce flower stalks, typically emerging from the crown in spring or early summer. These stalks are taller and more rigid than the edible leaf stalks, topped with clusters of small flowers. When a rhubarb plant flowers, it diverts significant energy away from developing edible leaf stalks towards reproduction. This process is sometimes referred to as “bolting.”
Late Season Growth and Senescence
After the primary harvest window, usually by mid-summer, rhubarb’s growth slows. The leaves may yellow or brown as the plant prepares for its next dormant period. As temperatures drop in late summer and fall, the plant continues to photosynthesize, building up energy reserves in its crown for the following year’s growth. The foliage will eventually die back completely with the onset of frost.
Care and Harvesting Practices Per Stage
During the plant’s dormant phase, minimal intervention is required. Late fall or early spring is an opportune time for planting new crowns or dividing overcrowded plants, ideally when roots are dormant. Established plants benefit from a layer of well-rotted compost or manure applied around the crown in late autumn or early spring to replenish nutrients.
As rhubarb begins its spring emergence, ensure adequate moisture, especially if rainfall is scarce. Once actively growing, a 3-4 inch layer of mulch around the plants helps conserve soil moisture and suppress weeds. Consistent watering is beneficial during dry periods, particularly during the rapid stalk development phase.
If flower stalks appear, remove them promptly by cutting them at their base. This redirects the plant’s energy into producing more edible leaf stalks rather than seeds, which can reduce vigor and yield. For newly planted rhubarb, do not harvest any stalks in the first year to allow the plant to become well-established. In the second year, harvest sparingly, taking only a few stalks.
From the third year onward, rhubarb can be harvested for 8 to 10 weeks, typically from late April through June or early July. Harvest stalks when they are 10 to 18 inches long and at least 3/4-inch in diameter by grasping the base and pulling with a gentle twist. After early July, or when stalks become thin, stop harvesting to allow the plant to build up energy reserves for the next growing season. Always leave at least one-third to one-half of the plant’s stalks to ensure enough foliage remains to support the crown.