Kalmus

Kalmus, commonly known as sweet flag, refers to Acorus calamus, a perennial aquatic plant in the family Acoraceae. It is native to temperate regions of Europe, Asia, and parts of North America, where it grows in wetlands and along streams. The plant is best known for its aromatic rhizomes, which have been harvested for culinary, medicinal, and perfumery uses for centuries.

It forms clumps of upright, grasslike leaves with a distinctive scent when crushed. Stems can reach about 60 to 120 cm in height. The inflorescence is a small, dense spike (spadix) that emerges above the foliage, often partially enclosed by a leaf-like bract. The underground rhizomes are thick and yellowish, from which new shoots arise.

It grows in wet habitats such as marshes, fens, riverbanks, and shallow ponds. It is native to Europe, Asia, and North America, but has been cultivated and naturalized in other regions. It spreads by creeping rhizomes and can form substantial stands in suitable moist soils.

Historically, kalmus rhizomes have been dried and used as a spice and flavoring agent in certain cuisines, and the essential oil derived from the rhizomes has been employed in perfumery and traditional medicine. In modern practice, however, the use of calamus oil and extracts is often restricted due to safety concerns about certain constituents.

Beta-asarone, a major constituent of calamus oil, has been linked to carcinogenic effects in animal studies. As a result, many countries regulate or prohibit calamus oil in consumer products, and some jurisdictions impose restrictions on its use as a food additive or dietary supplement. Regulation varies by region and product type.

For cultivation, kalmus prefers moist, fertile soils and full sun to partial shade. It propagates by division of the rhizomes and can be invasive in favorable conditions, requiring management where it is not desired. It is generally hardy in temperate climates, though frost sensitivity varies by cultivar.