Dietes grandiflora aka Wild Iris

Dietes grandiflora is an evergreen perennial in the iris family, Iridaceae. Its common names include large wild iris and fairy iris. It comes from South Africa, from the southern Cape to KwaZulu-Natal. Its native range includes southern and eastern coastal areas. Wild plants grow beside forests and beneath taller shrubs. They also grow on exposed slopes that face the sea.

Plants form large, upright clumps of dark green leaves. The sword-shaped leaves spread in fans around slender flower stems. These stems reach about 3 feet [0.9 metres] long. Garden plants reach 3.3–4.9 feet [1–1.5 metres] tall. Their spread reaches 0.3–1.6 feet [0.1–0.5 metres]. Chicago Botanic Garden gives a similar height of 5 feet [1.5 metres]. Plants can take two to five years to reach full size.

The flowers resemble irises and reach 0.33 feet [0.1 metres] across. Broad white outer segments carry yellow stripes near their bases. Dark marks also appear near the bases of these segments. The upright central segments are violet to violet-blue. Each flower lasts only a few days. New flowers open in waves through summer, sometimes weeks apart. The flowering season follows local seasons, so calendar months vary. Bees and other pollinators visit the blooms. Chicago Botanic Garden also lists interest for birds and butterflies.

Give plants full sun or some shade in a sheltered spot. They prefer moist soil that drains well. They also cope with poor soil and dry ground. Chalk, loam, and sand suit them across a broad pH range. The RHS rates their UK hardiness as H3. This suits coastal sites and other mild parts of Britain. Chicago Botanic Garden lists USDA zones 8–9. Under glass, use peat-free, loam-based compost with ample light and airflow. Feed monthly with a balanced liquid fertiliser. Reduce watering after bloom and keep dormant plants only slightly moist.

Use this plant in beds, borders, pots, or as a specimen. It also suits gravel gardens and sheltered courtyards. No routine pruning is needed. The RHS reports few usual pest or disease problems. Sow seed in spring or autumn at 13–15°C. Another option is to divide the rhizomes after flowering. New plants can be slow to settle in.