Perennial monocotyledon, stems 20-80 cm from thick rhizomes, buried or barely at soil surface, often forming large clumps.
Leaves mostly basal, 0.2-1 m long, 0.5-3 cm wide, in fan-shaped arrangement, broadly linear, about as long as flowering stem, usually purple at base, stem leaves few; flowers 6-8 cm wide.
Flowers blue-violet with darker veins, 6-8 cm wide, petals 3, erect, shorter than sepals, 2-5 cm long, 0.5-2 cm wide, sepals 3, 0.4-0.7 cm long, 2-3.5 cm wide, yellow-green hairy spot at base, pendant, petals and sepals narrowed at base; visited by hummingbirds, insect and/or bird pollinated; blooms May-July.
Fruit dry, 3-parted cylindrical capsule, 1.5-6 cm long, 0.5-0.8 cm wide, tip beaked, 3-angled, inner surface shiny brown (Levine 1995), splitting open by 3 valves to release thick, angular seeds during winter, probably water dispersed.
Wetland status: OBL.
Frequency in NYC: Occasional.
Habitat: Undisturbed marshes, pond edges. Planted in some wetland restorations and mitigations.
Notes: Pollen, nectar and corolla parts eaten by a specialized weevil, the flag beetle (Mononychus vulpeculus: Curculionidae) which spends its life on Iris versicolor (Lovell 1918; Bartlett 2007).