[Wikipedia] Uses - Medicinal, Crafts, Harmful Effects: Uses Drawing of a fertile stem of E. arvense, 10 cm as drawn. At the top is the strobilus, which consists of the axis (inside) and 15?20 horizontal circles of about 20 sporangiophores. Lower on the stem are two sheaths of merged microphylls. The stem has many strong lengthwise ridges. Medicine The plant contains several substances that can be used medicinally. It is rich in silicon (10%), potassium, calcium, manganese, magnesium and phosphorus, phytosterols, dietary fiber, vitamins A, E and C, tannins, alkaloids, saponins, flavonoids, glycosides and caffeic acid phenolic ester. The buds are eaten as a vegetable in Japan and Korea in spring. Recent research has shown limited evidence of anti-inflammatory, diuretic, antimicrobial, and antioxidant properties. [15] Craft production It was also once used to polish pewter and wood (gaining the name pewterwort) and to strengthen fingernails. It is also an abrasive. It was used by hurdy-gurdy players to dress the wheels of their instruments by removing resin build up.[16] Harmful effects Equisetum arvense is toxic to stock, particularly horses (link added by Mary Ann Machi)