Rhubarb is a unique perennial plant often categorized as a vegetable in botanical terms, yet it is almost exclusively prepared and consumed like a fruit. This plant is one of the first crops ready for harvest in the spring, recognized for its tart flavor and long, fleshy stalks. Many people believe the stalk must turn deep red before it is ready to eat, causing confusion when they encounter bright green stalks. This information clarifies whether green rhubarb is safe and fully ready for consumption.
Color and Rhubarb Readiness
The color of a rhubarb stalk, which can range from vivid crimson to pale speckled pink to solid green, is determined by the plant’s specific variety, not its maturity or ripeness. Certain cultivars are genetically programmed to produce green stalks even when fully developed and ready for harvest. For example, varieties like ‘Victoria’ and ‘German Wine’ are known for their predominantly green stalks, which are just as safe to eat as the red ones. The red pigmentation in other varieties is caused by the presence of a natural compound called anthocyanin. While a deeper red color may be visually appealing for culinary uses, it does not indicate a safer or more developed stalk. Relying on color alone is an unreliable indicator for deciding when to harvest.
How to Know When to Harvest
Since color is an unreliable indicator, the physical characteristics of the stalk are the best signs of readiness for harvest. A developed rhubarb stalk should be firm, crisp, and measure between 10 and 15 inches in length. Stalks that are thin or spindly should be left to grow further, as they have not yet reached their full potential. The harvest season generally runs from late spring through early summer, typically ending around the end of June to allow the plant to store energy for the following year.
The proper technique for harvesting involves selecting a stalk near the base of the plant, grasping it firmly, and twisting and pulling it away from the crown. This pulling method is preferred over cutting with a knife, as a cut stub left behind can become an entry point for rot or disease. It is also important to take only about one-third of the total stalks from the plant at any one time to ensure the plant remains vigorous and productive.
Rhubarb Safety and Toxicity
Regardless of the stalk’s color, public health and safety require strict differentiation between the edible stalk and the highly toxic leaves. Rhubarb leaves contain high concentrations of oxalic acid, a compound that can be poisonous if consumed. This compound is present in much lower, safe levels in the stalks, which is why only the stalks should ever be used for food preparation.
Ingesting the leaves can cause a condition known as hyperoxaluria, where excess oxalate is excreted in the urine, potentially leading to the formation of calcium oxalate crystals in the kidneys. Symptoms of consuming rhubarb leaves include stomach pain, vomiting, and diarrhea. In more severe cases, high-dose exposure can lead to kidney damage and even kidney failure, underscoring the necessity of removing the leaves entirely before cooking or eating the stalks.