Rhubarb is a unique perennial, botanically a vegetable, whose tart, fleshy stalks are commonly used as a fruit for pies and jams. Proper harvesting practices are important for the plant’s longevity and consumer safety. The edible stalks are surrounded by large leaves containing high concentrations of oxalic acid, a naturally occurring compound that is toxic if consumed. Understanding the correct time and technique for removal is necessary to maintain a healthy, productive patch for many years.
Identifying Harvest Readiness
The primary factor in determining harvest readiness is the age of the plant. Avoid harvesting any stalks during the first growing season to allow the crown and root system to fully develop energy reserves. In the second year, you may take a small, test harvest, but the plant should be harvested normally only from its third season onward.
A ready stalk should be plump, firm, and reach a length between 7 and 15 inches. The color of the stalk, which can range from ruby red to speckled green depending on the variety, is not an accurate indicator of ripeness. Focus instead on the physical size and condition, ensuring the stalk is thick and robust.
The general harvest season begins in late spring and typically runs for about eight to ten weeks, ending around mid-summer (late June or early July). Discontinue harvesting when new stalks begin to look noticeably thin or spindly. Thin stalks signal that the plant’s stored energy reserves are becoming depleted, and further harvesting could weaken the plant’s ability to survive winter dormancy.
The Proper Harvesting Technique
The mechanical technique used to remove the stalk is important for maintaining a healthy, productive plant. The recommended method is a twist-and-pull motion, rather than cutting the stalk with a knife or shears. Grasp the stalk firmly near the base, then lean it to one side while gently twisting and pulling it upward.
The stalk should separate cleanly from the crown, removing the entire stalk tissue and preventing a stub from remaining. Leaving a cut stub creates an open wound where moisture can collect, potentially inviting diseases like crown rot. The pull-and-twist method encourages the plant to regenerate new stalks more quickly.
The amount of material removed is crucial for the plant’s vigor. Never harvest more than one-third to one-half of the fully developed stalks from a single plant during a harvest period. This practice ensures enough foliage remains to support photosynthesis, which creates the energy reserves for the following season.
Immediately after removing the stalk, use a sharp knife to trim the large leaf blade off at the stem end and promptly discard it. This prevents accidental consumption of the toxic leaves and keeps the leaves from drawing moisture out of the edible stalk tissue through transpiration. The leaves are safe to add to a compost pile, as the toxic compounds break down naturally.
Post-Harvest Plant Maintenance
Once the harvest season ends in mid-summer, all remaining stalks and foliage should be left undisturbed. These large leaves continue to perform photosynthesis throughout the late summer and early fall, generating and storing the carbohydrates needed in the crown and roots. This period of rest is necessary for the perennial to recharge its underground reserves and produce a strong harvest the next spring.
Regular watering is important, especially during periods of high heat or drought after the harvest has concluded. Rhubarb requires consistent moisture to maintain the health of the remaining foliage and support the energy storage process leading into dormancy. Insufficient water can stress the plant and reduce its productivity in the subsequent year.
The plant benefits from a light application of fertilizer, such as a balanced granular formula or well-rotted compost, applied in early spring when growth resumes. Rhubarb is a heavy feeder that requires significant soil nutrients to develop large leaves and thick stalks.
If flower stalks begin to emerge during the growing season, remove them immediately by pulling or cutting them off at the base. Allowing the plant to flower diverts energy away from stalk production and reduces the overall vigor of the plant.