Rhubarb is a perennial vegetable that is often treated as a fruit in the kitchen. Knowing when to pick the edible stalks, or petioles, ensures the best flavor and texture while maintaining the health of the parent plant. Readiness is signaled through a combination of visual cues and seasonal timing.
Visual and Size Indicators of Readiness
The most reliable indicator that a rhubarb stalk is ready for picking is its size and robustness. Mature stalks, which are full of flavor, typically measure between 10 to 18 inches in length. Focus on the caliper, or thickness, as this is a better measure of maturity than the overall height. Thin, spindly stalks should be left to continue growing, as their removal may weaken the plant.
The color of the stalk is not a definitive measure of readiness. Rhubarb cultivars vary widely; some mature into a deep crimson red, while others are naturally speckled pink or vibrant green when ready. All colors are edible once the stalk is properly sized. The variation is due to anthocyanin pigments, not sugar content or ripeness. A healthy plant will also display large, fully unfurled leaves at the top of the stalk.
Seasonal Timing and Stem Texture
Rhubarb is a cool-season plant, and the main harvest window typically occurs in late spring and early summer, generally from April through June. The first stalks that emerge in the spring are often the most tender and flavorful. As the season progresses and temperatures rise consistently above 75°F, the stalks tend to become tougher and more fibrous.
A tactile test provides the final confirmation of readiness, as a ripe stalk should feel firm and crisp. When gently bent near the base, a mature stalk will snap cleanly, much like celery. Stalks that are limp, rubbery, or difficult to break have likely passed their prime and may be woody or stringy.
Harvesting must cease by mid-summer, generally around the end of June or early July, to ensure the plant can recover. Allowing the foliage to remain during the hottest months permits the perennial to photosynthesize and store energy in its root crown for the following year. Overly mature stalks left late in the season often become woody and less palatable.
Safe Harvesting Techniques
The correct method for removing a mature stalk is to pull and twist it, rather than cutting it with a knife or shears. Grasp the stalk firmly near the soil line and pull it slightly to one side while twisting upward. This technique ensures the entire stalk separates cleanly from the crown, the underground base of the plant.
Pulling the stalk is preferred because cutting can leave a small stub that may decay, creating an open wound through which disease or rot can enter the crown. Once the stalk is removed, the large leaf blade must be trimmed off immediately to prepare the edible portion of the plant.
The leaves of the rhubarb plant must never be consumed. Rhubarb leaves contain high concentrations of oxalic acid, a compound that is toxic to humans. Ingesting the leaves can lead to symptoms ranging from gastrointestinal distress to kidney damage. Only the stalk, or petiole, is edible, and the leaves should be discarded or safely composted.