Rhubarb is a perennial vegetable, often treated as a fruit in cooking, but only the long, firm stalks (petioles) are edible. The large, triangular leaves are toxic and must never be consumed. Harvesting rhubarb in August is generally not recommended, as this period falls outside the ideal picking window. Harvesting this late significantly compromises the plant’s health and degrades the quality of the stalks. The plant needs time to recover and store energy for the following spring, ensuring the long-term vigor of the rhubarb patch.
The Ideal Rhubarb Harvesting Season
The optimal time to harvest rhubarb begins in early spring, often April or May, and typically lasts for about eight to ten weeks, concluding by late June or early July. This early season is when the stalks are at their most tender, containing the best flavor and texture. Rhubarb stalks are ready to be picked when they reach a length of at least ten inches and feel crisp and firm to the touch.
Determining ripeness should not rely solely on color, as some varieties naturally produce green stalks, while others are deep red or pink. The correct method for removing the stalks is the “twist and pull” technique, which is healthier for the plant than cutting. To do this, grasp the stalk near the soil line, twist it gently, and pull it away from the plant’s crown.
Cutting the stalk with a knife or shears leaves a stub that can become an entry point for diseases like crown rot. The twisting motion ensures the stalk cleanly separates from the base, promoting a faster, cleaner healing process. When harvesting, take only about one-third of the total stalks from an established plant. This ensures enough foliage remains to support the plant’s growth.
Why Harvesting Stops in Mid-Summer
Harvesting stops in mid-summer, usually by late June or early July, primarily to allow the plant to prepare for dormancy. While some older beliefs suggest the entire plant becomes poisonous, the main issue is plant health and stalk quality. As summer progresses, the stalks become woodier and thinner, leading to a tougher texture and less desirable flavor for cooking.
The cessation is also connected to the plant’s chemistry, specifically the concentration of oxalic acid. While the stalks always contain a safe amount, the concentration can increase toward the end of the season. This increase, combined with decreased sugar content and tougher texture, makes August stalks less appealing to eat.
The plant’s natural growth cycle requires it to shift focus from producing edible stalks to storing energy for winter. By mid-summer, the plant channels sugars and nutrients down into its underground crown. Harvesting during August interferes with this energy storage process. This directly affects the plant’s ability to survive the cold and produce a strong yield the following spring.
Protecting Your Plants for Future Harvests
Ceasing the harvest in August ensures the long-term health and productivity of your rhubarb patch. Allowing the leaves to remain maximizes photosynthesis, which builds the carbohydrate reserves needed for survival. These reserves are stored in the crown, the thick underground structure that will produce next year’s stalks.
If you continue picking late into the season, you deplete the crown’s reserves, causing it to weaken. This over-harvesting results in a smaller yield and thinner, less vigorous stalks the following spring. Instead of picking, gardeners should maintain a healthy environment for the plant by watering it deeply during dry periods.
Allowing the plant to rest in August ensures it can enter winter dormancy with a full energy bank. Any flower stalks that emerge should be cut off immediately to prevent the plant from diverting energy away from the crown and into seed production. By mid-to-late autumn, the leaves will naturally begin to die back, signaling the plant is prepared for the next growing season.