Wild rhubarb, a plant found in natural settings, is recognized by its large leaves and sturdy stalks. The term can be confusing, as it’s sometimes used for plants like Common Burdock, which differ botanically. For culinary use, “true rhubarb” belongs to the Rheum genus, known for its tart, edible stalks.
Understanding Wild Rhubarb Edibility
Only the stalks of true rhubarb (Rheum species) are safe to eat. These fibrous, often red or green petioles are the sole edible part. The leaves, roots, and flowers contain high concentrations of oxalic acid, making them toxic. Ingesting oxalic acid can cause various adverse effects.
Symptoms of rhubarb leaf poisoning include vomiting, diarrhea, and abdominal pain. More severe cases can involve a burning sensation in the mouth, difficulty swallowing, nausea, and blood in vomit. Oxalic acid can also interfere with calcium absorption and lead to calcium oxalate crystal formation in the kidneys, potentially causing kidney stones or kidney failure. While fatalities are rare, they have been reported from consuming very large quantities of the leaves. In contrast, Common Burdock, sometimes mistaken for wild rhubarb, has leaves that are safe to consume.
Key Identification for Wild Rhubarb
Accurate identification is crucial when harvesting wild rhubarb. True rhubarb (Rheum species) has large, often heart-shaped to triangular leaves that are smooth, glossy, and have distinct red or thick veins. Its solid stalks grow directly from a rootstock and can be green to deep red, often with reddish bases.
Common Burdock (Arctium minus) is a frequent look-alike. While burdock also has large, broad leaves, its leaves are matte with a slightly velvety or woolly underside, unlike true rhubarb’s glossy leaves. Burdock stalks are hollow, whereas true rhubarb stalks are solid. Burdock plants grow more vertically from a central stem and, in their second year, produce purple thistle-like flowers that develop into distinctive burrs. These differences in leaf texture, stalk structure, and the presence of burrs are reliable indicators for differentiation.
Safe Harvesting and Preparation
Harvest true rhubarb stalks in spring and early summer, from April until late June or early July. Stalks are ready when they reach 8 to 15 inches. The quality is generally best before the plant sends up a flower stalk. Stop harvesting by mid-July to allow the plant to store energy for the next growing season.
To harvest, grasp plump, crisp stalks near their base and twist them away from the plant. This method encourages regrowth and helps prevent diseases. For the plant’s health, take no more than one-third of the stalks at a time, especially from younger plants.
Immediately trim and discard the toxic leaves. Rinse the stalks thoroughly. Peeling is usually not necessary unless the stalks are particularly thick or fibrous. Chop cleaned stalks into 1/2-inch to 1-inch pieces for baking, jams, or stewing.
Important Safety Considerations
Always ensure accurate identification when consuming wild plants. Never consume the leaves, roots, or flowers of true rhubarb due to their high concentration of oxalic acid; even small amounts can cause gastrointestinal distress, and larger quantities can lead to kidney damage.
Individuals with pre-existing kidney conditions or those prone to kidney stones should exercise caution or avoid rhubarb, as oxalic acid can exacerbate these issues. While stalks are safe, consume them in moderation. If you doubt a plant’s identity or experience poisoning symptoms after consumption, contact a local poison control center or medical professional immediately.