Iris tuberosa aka Snake's Head Iris

Iris tuberosa belongs to the iris family, Iridaceae. It is a tuberous perennial: it grows from tubers and lives for years. Its native range starts in southeastern France. It extends to western and northern Türkiye. There, it grows in a subtropical climate. It is not native to Britain or Ireland. Its common names include snake's head iris, black widow and onion iris. Hermodactylus tuberosus is another name for the same species.

This bushy plant is deciduous, which means it sheds its leaves. Garden height and spread range from 0.3–1.6 feet [0.1–0.5 metres]. Plants take two to five years to reach full size. The leaves are narrow and lance-shaped, with a grey-green cast. They emerge in winter or early spring. Flower stems reach about 1.3 feet [0.4 metres], below the leaf tips. The flowers have greenish-yellow standards, the upright flower parts. Their falls, the parts that hang down, are dark. These range from purple-brown to almost black. Chicago Botanic Garden uses the older name for this plant. It lists bloom time as March through June.

Give this iris full sun and shelter on a south-facing site. It suits chalk, loam or sand that drains well. The RHS lists neutral to alkaline soil as suitable. Its planting guide favours alkaline soil with a fair level of nutrients. It also calls for water to drain away very fast. Plant the tubers in autumn, about 0.33 feet [0.1 metres] deep. Dry soil in summer helps the plant flower. The RHS gives it a hardiness rating of H5. Chicago Botanic Garden lists USDA zones 7–9 under its other name.

This iris suits rock gardens, beds, borders and informal cottage gardens. The RHS also lists wildflower meadows, banks and slopes. It suits Mediterranean-style planting, too. You can cut its flowers for use indoors. The blooms sit below the leaf tips, not above them. Pale standards stand out against the dark falls. You do not need to prune this plant. Divide plants in early summer, once the leaves have died back. By then, the plant has lost the season's leaves.

Slugs, snails and thrips may attack the plant. Viruses spread by aphids can cause problems, too. Other risks include bacterial soft rot and grey moulds. These may occur, but not every plant will suffer. Eating this iris can harm both people and pets. Do not treat its tubers or other parts as food. The RHS advises gloves and other gear to protect you when handling it.