Rhubarb is a perennial vegetable often prepared and enjoyed like a tart fruit, making it a highly anticipated ingredient for pies, sauces, and jams across Wisconsin. Harvesting requires specific timing and technique to ensure the health of the perennial crown and a bountiful yield. This guide focuses on when and how to collect the edible stalks.
Determining the Start of the Rhubarb Season
The first harvest in Wisconsin generally begins when spring weather provides enough warmth and moisture to produce robust stalks. This period typically falls between late April and early May. Stalks are ready when they are firm, crisp, and have reached a length of approximately 10 to 15 inches.
The color of the stalk, whether deep red or a lighter green, is not a reliable indicator of ripeness, as this characteristic is determined by the specific rhubarb cultivar. A light harvest is recommended when the plant is young, specifically for plants in their second or third season after planting. Taking only a few stalks allows the plant to establish a stronger root system before the full harvest period begins.
The Correct Way to Pull Rhubarb Stalks
Harvesting should always involve pulling the stalks, rather than cutting them with a knife or shears. This technique encourages the plant to regrow and prevents a major entry point for disease. To properly remove a stalk, firmly grasp it near the base at the soil line.
Apply a gentle twist and pull motion, leaning the stalk slightly to the side until it cleanly separates from the crown. If a stalk is cut, the remaining stub can decay, creating a wound that makes the plant susceptible to crown rot and other pathogens. To ensure the perennial’s long-term health, never remove more than two-thirds of the total stalks at any one time, leaving plenty of foliage intact for photosynthesis.
Understanding When the Harvest Must End
Stopping the harvest allows the plant to store energy for the following year. The traditional guideline for ending the rhubarb season is around the Fourth of July, which marks the transition into the summer heat. Continuing to harvest past this mid-summer deadline severely weakens the plant’s crown and reduces its vigor for the next spring.
As summer temperatures rise in Wisconsin, the stalks naturally become thinner, tougher, and more woody. This change in texture and flavor makes the late-season stalks less desirable for culinary use. Allowing the remaining leaves to gather sunlight through the late summer and early fall is necessary for transferring carbohydrates to the roots for winter dormancy.
Essential Safety Information
Only the leaf stalks of the rhubarb plant are safe for consumption. The leaves contain high concentrations of oxalic acid, a naturally occurring substance that is toxic to humans and pets, even after cooking.
Ingestion of the leaf blade can lead to mild gastrointestinal distress. Larger amounts can cause serious problems like kidney stones or kidney failure due to the buildup of calcium oxalate crystals. After harvesting, immediately trim the leaves from the stalks and discard them. While the leaves are toxic, they can be safely added to a compost pile, as the toxic compounds will break down during the composting process.