Iris versicolor aka Purple Iris

Iris versicolor, or northern blue flag, belongs to the iris family. This perennial grows in central and eastern North America. Its range runs from Manitoba east to Nova Scotia. It extends south into Virginia and parts of the Midwest. Wild plants grow in marshes, swamps, wet meadows, and ditches. They also grow along lakes, rivers, and other wet shores.

The plant forms clumps from tough rhizomes that creep slowly. Garden plants reach about 2–3 feet (0.6–0.9 metres) tall. RHS gives an upper height of 3.3 feet (1 metre). Clumps can spread to 2.5 feet (0.76 metres) wide. Blue-green leaves stand upright or bend in a slight arch. Their narrow, sword-like blades form fans at the base. Leaves reach about 2 feet (0.6 metres) long. They have smooth edges and no hairs. The plant loses its leaves in the dormant season.

Bare or branched stems carry several flowers above the leaves. Each stalk bears three to five blooms in late spring. Flowering can continue into early summer, with May–June the main period. Flowers are blue to purple, though some blooms approach white. Each flower has three upright standards and three spreading falls. Purple veins mark a white patch around a yellow centre. Blooms can reach about 0.33 feet (0.10 metres) across. The fruit is a capsule. The flowers also suit cutting for indoor use.

Grow this iris in full sun, with partial shade tolerated. It needs soil that stays moist or wet. Deep, humus-rich soil suits it, with acid or neutral pH. It can grow in clay, loam, or sand. Plants also tolerate shallow standing water over their roots. Pond edges, bog gardens, and damp borders provide suitable sites. Groups can form colonies in wet areas over time. Deer tend to leave the plants alone. Sources give USDA zones 3–9 or the narrower 5–9 range. RHS rates its UK hardiness as H7. Divide clumps after flowering; wear gloves when handling the rhizomes.

Care needs are low, but several pests can cause damage. These include aphids, iris borers, thrips, slugs, and snails. Diseases include soft rot, other rots, blight, and leaf spot. Aphids can also carry viruses, and grey mould may occur. No edible uses are known. Eating the plant can harm people and pets. Rhizomes hold the highest concentration of toxic compounds. Sap, seeds, and rootstock can irritate skin. Reported traditional uses include root remedies and weaving with leaves. Those medicinal uses do not make the plant safe to eat.