Iris setosa aka Arctic Blue Flag

Iris setosa is a perennial in the iris family, Iridaceae. Common names include Arctic iris, beachhead iris, and bristle-pointed iris. Its native range spans northern European Russia to northern and central Japan. It also grows wild from Alaska into western Canada. It is not native to Britain or Ireland. Wild plants grow in wet, peaty meadows and along rivers. They also occur in open woods and some brackish bogs.

This iris grows from rhizomes and forms upright tufts. In gardens, it reaches about 1.6–3.3 feet [0.5–1 metre] tall. Its spread ranges from 0.3–1.6 feet [0.1–0.5 metres]. The RHS describes flowering plants around 3 feet [0.9 metres] tall. Plants take two to five years to reach full size. The green leaves have a clear raised midrib. They die back rather than stay green through winter.

Blue to purple flowers appear in late spring. Each bloom spans about 0.2–0.3 feet [0.06–0.09 metres]. The small upright petals, called standards, contrast with broad, rounded falls. This shape gives the flowers their main visual appeal. The plant suits flower beds, borders, and informal cottage gardens. Gardeners can also grow it for cut flowers. PFAF lists bog gardens, sunny woodland edges, and dappled shade as settings.

For cultivation, the RHS recommends loam that drains well. The soil should be neutral to slightly acid. Choose full sun or partial shade. This advice differs from the wet sites found in its wild range. The RHS gives it the cold-hardiness rating H7. PFAF lists USDA zones 4–8. Sow seed in pots within a cold frame during spring or autumn. Divide rhizomes from midsummer through early autumn. Remove dying leaves in autumn and spent stems after bloom.

Slugs, snails, and thrips may attack this iris. Diseases include viruses spread by aphids, soft rot, and grey mould. The RHS warns that eating it can harm people and pets. Wear gloves when handling it, as skin reactions can occur. PFAF reports starch from roots and a coffee substitute from roasted seeds. These recorded uses do not remove the warnings about eating it. PFAF also records root preparations used as laxatives. Petals provide a dye, though the source gives no colour. Treat these as reported uses, not proof of safety.