Iris douglasiana aka Marin Iris

Iris douglasiana, or Douglas iris, belongs to the iris family, Iridaceae. This evergreen perennial comes from Oregon and California. It grows in open woods, fields, and grassy slopes. It also grows in other open sites across varied soils. Underground rhizomes support its leafy growth. In gardens, it forms a bushy plant with year-round leaves.

Garden plants reach about 1.6–3.3 feet (0.5–1 m) tall. The RHS also describes plants about 2.3 feet (0.7 m) tall. Their spread reaches about 1.6 feet (0.5 m). Plants take two to five years to reach full size. The narrow leaves are dark green, and flower stems often branch. Purple or lavender-blue blooms open in late spring. Each flower can span about 0.33 feet (0.1 m). The falls often show a white patch at their base.

Grow Douglas iris in full sun or part shade. Choose a sheltered spot with soil that drains well. Moist soil suits it, but good drainage remains important. It grows in clay, loam, or sand. Acid to neutral soil suits it best. The RHS notes some tolerance of drier and more alkaline soils. It rates this species among the easiest Pacific Coast irises. Its UK hardiness rating is H6. Plants For A Future lists USDA zones 6–9.

This iris suits coastal gardens, courtyards, and informal flower beds. It can also serve as ground cover near woodland edges. Its evergreen leaves provide cover beyond the flowering season. Grow new plants from seed or divide them in spring. Remove dead leaves and cut spent flower stems after bloom. Slugs, snails, and thrips may attack it. Possible diseases include viruses spread by aphids, bacterial soft rot, and grey mould.

Plants For A Future records no known food or medicinal uses. The plant is harmful when people or pets eat it. Wear gloves and other protection when handling it. Its leaves have supplied fibre for cord and rope. Indigenous North American makers used fibres from the leaf edges. The fibre makes strong, flexible cord, though gathering it takes much work. The leaves can also supply fibre for paper. Harvest takes place in summer after bloom, before processing into pale tan paper.