Iris spuria aka Blue Iris

Iris spuria is a beardless perennial in the iris family. Its common names include blue iris and salt marsh iris. It grows from rhizomes and forms upright, spreading clumps. Sources place its native range across Europe and southwestern Asia. Missouri Botanical Garden also includes northern Africa, from Algeria eastward. This species is not native to Britain or Ireland.

Garden plants reach about 1.6–3.3 feet [0.5–1 metre] tall. Some stems reach 5 feet [1.52 metres]. Cold winters can limit stem height. Reported spreads range from 0.3–3 feet [0.1–0.91 metres]. The narrow leaves stand upright and look grey-green to blue-green. They can reach 3–4 feet [0.91–1.22 metres] long. Their edges are smooth, and their surfaces lack hairs. Leaves die back in late summer after flowering and seed set.

Flowers appear from May to July, spanning spring and summer. Branched stems can carry as many as five blooms. Their narrow falls and standards give them a slim shape. Blue-purple and lilac flowers may have yellow ridges on the falls. The species also shows white, yellow, wine, and brown shades. Butterflies visit the blooms. Brown seed capsules follow the flowers and remain into autumn. Each long capsule has six grooves and a beaked tip. Inside are angular seeds with a pale brown coat.

Plant it in full sun for better bloom and disease resistance. It also tolerates some shade. Give it fertile soil with good drainage and ample organic matter. Neutral to slightly alkaline soil suits it well. RHS also lists acid soil as suitable. Keep moisture steady while the plant grows, but avoid wet ground. Summer dormancy can reduce its need for water after bloom. Amend heavy clay to improve drainage. Sources rate it for USDA zones 5–9, with Chicago listing 4–9. RHS gives it a UK rating of H6. Use it in sunny borders, cutting gardens, or mass plantings. Propagate it by seed or division.

Iris borers, weevils, slugs, snails, and thrips can damage plants. Soft rot, crown rot, leaf spot, and viruses also occur. Grey mould and mustard seed fungus pose further risks. Remove diseased growth and clear dead foliage to reduce problems. This iris is harmful to people and pets when eaten. Rhizomes hold the highest concentration of its toxic compounds. Poisoning can cause drooling, vomiting, diarrhoea, and lethargy. Contact with the plant can also irritate skin.