Botanical atlas

American Sweet Flag

Acorus americanus

Long before it had a Latin name, this marsh-loving iris relative was known to the Cree, Ojibwe, Blackfoot, and many other nations as rat root, a small chewed piece of rhizome said to steady the traveler against cold, fatigue, and hunger on long journeys or portages. It moved along extensive trade routes far beyond its wetland range, carried and exchanged as something worth having, a sign of how highly its warming, spicy root was regarded. Bundles of the leaves and root were also kept for ceremony and for the sweet, ginger-like fragrance that clings to the hands after handling it. Its more recent history includes caution as well as reverence, since twentieth century research into its aromatic compounds led food regulators to draw firm lines around how the plant, and its close relatives, should and should not be used.

Safety.

The FDA prohibits internal use of calamus root because of documented toxicity and carcinogenicity in animal studies, and in larger amounts it has historically caused nausea, vomiting, and hallucinogenic effects, plus possible interactions with sedative or psychoactive medications; it is not safe in pregnancy or for children. It also grows alongside genuinely toxic look-alikes like blue flag iris and is easily confused with its even more potent relative, Acorus calamus, so it should not be gathered or used as food or medicine.