Sweet flag, Acorus calamus, is a grass-like perennial that can grow up to 2 meters or 6.6 feet high. Sweet flag, along with the common cattail, thrives in wet areas like the edges of streams, ponds, and lakes. The thick, erect leaves resemble an iris. The flowers are greenish brown cylinders covered in little rounded spikes, but they rarely flower.

The roots spread horizontally very close to the surface of the soil, and are a known favorite snack of the muskrat. Sweet flag spreads by means of rhizomes, a subterranean stem, thickened with deposits of food reserves. These specialized plant stems produce shoots and root systems that will develop into new plants. Rhizomes enable plants to do two things, propagate vegetatively and to perennate -- survive an unfavorable season -- hidden underground, protected from adverse elements.

The Cree Indians used sweet flag for medicinal purposes, e.g., an analgesic for toothaches or headaches, a disinfectant for teeth, relief for exhaustion or fatigue and as a cure for hangovers. Other North American Indians used the plant to treat coughs and diabetes. The Sioux used the whole plant, making aromatic garlands from the leaves and using the roots to make tea to treat bowel pains or placing chewed root on the skin to cure illness. Sweet flag has also been used by the Chinese to reduce swelling and to help relieve constipation. In India, the root was used to cure fevers, asthma, and bronchitis. The ancient Greeks also used the plant in many traditional remedies. The root was even mentioned in the Bible (Exodus 30: 22-25) as one of the ingredients of the "holy anointing oil." Despite the plants rich history, it has been banned by the FDA as a food additive because it has proven to be carcinogenic in laboratory rats.