Iris japonica aka Butterfly Flower

Iris japonica, or fringed iris, belongs to the iris family. Its native range runs from China to Myanmar and Japan. It grows along woodland edges, on slopes, and near streams. This evergreen perennial spreads through thin, creeping rhizomes. New leaf fans form as the rhizomes reach outward. It suits shade gardens and can form a low ground cover.

Garden plants often stand 0.8–1 foot (0.25–0.3 metres) tall. They spread about 1–1.5 feet (0.3–0.46 metres) wide. RHS gives an upper size of 1.6 feet (0.5 metres). The green, sword-shaped leaves rise from the plant's base. They reach 1–1.7 feet (0.3–0.5 metres) long, with arching tips. Their upper sides have a slight gloss. The lower sides look paler and duller. Slender green stems have smooth surfaces.

Flowers appear in spring, with timing varying among sources. NC State lists April to May; Missouri Botanical Garden lists May to June. Each bloom spans about 0.16 feet (0.05 metres). The flowers resemble small orchids, with white to pale blue or purple tones. The broad outer segments, called falls, have fringed edges. Purple spots and raised yellow or orange crests add contrast. Three smaller inner petals sit above the falls.

Partial shade suits this iris, though it tolerates deeper shade. RHS also lists sun for sheltered sites with moist soil. Give it humus-rich soil that drains well. It accepts clay, loam, or sand across a broad pH range. It tolerates some drought, but prefers moderate moisture in cultivation. Wet winter soil can cause root rot. Missouri Botanical Garden lists USDA zones 7–9; RHS rates it H4. Cold sites may need a sheltered spot. Deer and rabbits tend to leave it alone. Its spreading growth suits woodland beds and naturalized areas. Sources do not describe it as invasive.

Slugs, snails, and thrips may damage plants. Other risks include aphid-borne viruses, soft rot, and grey mould. Remove dying leaves in autumn and spent flower stems after bloom. Divide rhizomes from midsummer into early autumn, or raise plants from seed. This iris harms people and pets if eaten. Wear gloves when handling it. PFAF reports edible starch from the root and traditional medicinal uses. These records do not make it safe to eat.