Iris prismatica, the slender blue flag or cubeseed iris,[2] is a plant species native to parts of the southern and eastern United States from Maine south to Alabama, as well as to the Canadian provinces of Ontario and Nova Scotia.

[3][4][5] Iris prismatica is a perennial herb spreading by means of rhizomes that are close to the surface of the soil.

Flowering stalks can reach a height of 80 cm.

[6][7][8][9][10] It tends to grow in swampy,[2] wet conditions,[3] and within the United States, it is currently state listed as 'threatened' in Maine, New Hampshire, New York, and Tennessee, and state listed as 'endangered' in Maryland and Pennsylvania.

[11] It is cold hardy to USDA Zone 3.