Numerous terrestrial species are introduced into many countries; many aquatics are established beyond botanical gardens, etc. Iris pseudacorus L. is introduced into the United States from Europe.
Iris douglasiana Herbert and I. missouriensis Nutt. are regulated in California (United States); I. pseudacorus is regulated in Vermont (United States).
Perennial. Creeping rhizome. Leaves rigid, flat, smooth and elongate-linear, distichous, equitant, overlapping each other but appearing to be in a rosette. Inflorescence a solitary flower or panicle. Flowers large, showy, subtended by a spathe-like bract; perianth of 6 tepals in 2 similar series; outer series deflexed, inner series erect. Dispersal by rhizome division and seeds.
wet ground and littoral region of lakes, swamps, and rivers
A genus containing over 300 species and many cultivated varieties. Most aquatic species belong to the section Apogon.