A graceful, sword-leaved plant similar to the garden iris, with showy, down-curved, violet, boldly veined sepals. Several violet-blue flowers with attractively veined and yellow-based sepals are on a sturdy stalk among tall sword-like leaves that rise from a basal cluster. Flowers may be any shade of purple, but are always decorated with yellow on the falls. Grows 2-3 ft. tall.
This is a showy native iris of northeastern wetlands. Insects attracted to the sepals must crawl under the tip of a style and brush past a stigma and stamen, thus facilitating pollination. A similar southern wetland species, occurring from Virginia to Florida and Texas, is Southern Blueflag (I. virginica). It is a smaller plant, to 2' (60 cm) tall, with bright green leaves that often lie on the ground or water. A coastal, brackish-water species, Slender Blueflag (I. prismatica) has extremely narrow, grass-like leaves that are less than 1/4" (6 mm) wide; it occurs from Maine to Georgia and Tennessee. The name "flag" is from the middle English flagge, meaning "rush" or "reed."