Rhubarb is an herbaceous perennial vegetable, valued not for its leaves, but for its tart, fleshy leaf stalks (petioles), which are harvested in the spring. While the plant is known for its hardiness, cultivating the thick, robust stalks prized for cooking requires targeted care and environmental optimization. Maximizing stalk thickness involves a specific long-term strategy, focusing on initial establishment, intensive annual feeding, energy management, and periodic plant rejuvenation.
Establishing the Ideal Growing Environment
Rhubarb requires a location receiving at least six hours of direct sunlight daily. Plants in warmer climates benefit from afternoon shade to reduce heat stress, as this light exposure drives the photosynthesis that fuels massive stalk growth.
The plant’s large root system demands deep, rich, well-drained soil, since crowns are highly susceptible to rot in waterlogged conditions. Before planting, prepare the site by tilling or forking the soil to a depth of at least two feet to accommodate root development. Mixing in ample organic matter, such as aged compost, improves drainage and helps retain moisture. A slightly acidic to neutral soil pH, ideally between 6.0 and 6.8, supports optimal nutrient uptake.
Strategic Feeding for Maximum Stalk Thickness
Rhubarb is considered a heavy feeder, meaning the production of large, vigorous stalks requires a consistent and substantial supply of nutrients. Nitrogen is particularly important for promoting the rapid vegetative growth that results in thick petioles. The most effective feeding strategy involves annual applications of high-nitrogen organic matter, specifically well-rotted manure or compost.
Applying a thick layer of aged manure, about two to three inches deep, around the base of the plant in early spring or late fall provides a slow-release nutrient source. This organic mulch also helps suppress weeds and maintain consistent soil moisture. Additionally, a side-dressing of a balanced commercial fertilizer can be applied in early spring before the stalks fully emerge. This dual approach ensures both immediate and sustained nutrient availability, supporting the rapid cell expansion required for maximum stalk width.
Energy Redirection: Managing Flowers and Buds
To ensure the plant’s energy is channeled exclusively into stalk production, energy redirection must be actively managed. Rhubarb plants naturally bolt, or send up a flower stalk, which diverts valuable resources away from the edible petioles. This flowering is often triggered by age, environmental stress, or variety-specific tendencies.
Prioritizing vegetative growth requires the immediate removal of any flower stalks as soon as they become visible. These stalks are easily identified as they are thicker and more upright than leaf stems, often topped with a dense bud. Cutting the entire stalk off at the base near the crown prevents the plant from wasting energy on seed production. Furthermore, new plants should not be harvested at all in their first year, allowing the crown to establish a robust root system capable of supporting consistently thick stalks in subsequent seasons.
Maintaining Vigor Through Division and Rest
Long-term productivity and stalk thickness depend on periodically rejuvenating the perennial crown through division and respecting the plant’s natural dormancy cycle. Over a period of five to eight years, the rhubarb crown can become overcrowded, leading to a noticeable reduction in stalk size and overall plant vigor. Dividing the crown is necessary to relieve this congestion and promote renewed, healthy growth.
The best time for division is when the plant is fully dormant, typically in early winter or late fall after the foliage has died back, or in early spring. The entire crown should be carefully lifted from the soil and cut into several pieces, ensuring each section retains at least one healthy bud and a good portion of the rhizome. Ceasing harvest late in the season, usually by mid-summer, ensures the root system can store enough carbohydrates for a strong start and thick stalks the following spring.