Rhizomer slender, green. Leaves flat, 1.5-2.5 cm wide, drooping, 50-60 cm long. Stems 70-90 cm tall with spathes at several internodes. Flowers 5.5- 6.5 cm wide, copper-red to orange; late spring. Perianth tube 2-2.5 cm long; falls and standards similar, drooping. Style branches obliquely erect. Syn. I. cuprea Pursh.

Mississippi valley of USA.

I. missouriensis Nutt., Western Blue Flag from W USA has a wiry rhizome. Leaves linear to 10 mm wide. Stem branched, 45-70 cm tall. Spathes papery with green keel. Flowers 2-3; spring. Falls narrow-oblanceolate 5-6 cm, white or pale violetblue with purple veins and often a yellow signal. Standards 5.5 cm, violet. Style branches 2 cm long.

Source: Cooke, D. (2005). Iridaceae. In: Spencer, R.. Horticultural Flora of South-eastern Australia. Volume 5. Flowering plants. Monocotyledons. The identification of garden and cultivated plants. University of New South Wales Press.