Ferraria crispa aka Black Flag

Ferraria crispa is a tender plant in the iris family, Iridaceae. It is a perennial, so it lives for several years. It comes from the southwestern and south-southwestern Cape of South Africa. The climate there is subtropical. Its common names include starfish iris, curled ferraria, and krullefjie. The name Ferraria undulata means the same species. It grows from corms below ground and sheds its leaves each year.

The plant grows upright, stays narrow, and takes little space. It reaches about 1.5 feet [0.45 metres] tall. The listed garden height range reaches 1.6 feet [0.5 metres]. Its spread reaches about 0.3 feet [0.1 metres]. Long, thin leaves clasp the stems at their bases. Each leaf can grow about 0.8 feet [0.25 metres] long. Plants reach their full size within one to two years.

Flowers bloom in spring and face up above the leaves. The petals have wavy edges and green or cream backgrounds. Purple and brown spots mark the blooms. Each flower can span about 0.16 feet [0.05 metres]. The blooms have a bad smell. Their marked petals and curled edges give them their main appeal. The RHS suggests growing this plant in greenhouses and conservatories. A temperate greenhouse gives it the shelter it needs from frost.

Give plants full sun and a site with shelter. Choose a site that faces south or west. Use sandy or loamy soil that stays moist but drains well. The soil can be acid, neutral, or alkaline. Plant corms in autumn, about 0.5 feet [0.15 metres] deep. Under glass, use a border or a deep pot. Fill pots with peat-free compost based on loam, and add grit. Give moderate amounts of water and full light during winter growth. Feed once a month with a balanced liquid fertiliser. Keep corms dry through summer, not moist all year.

The RHS gives it a hardiness rating of H2. It copes with cool weather, but not with freezing. Chicago Botanic Garden lists USDA zones 9–10. It needs no routine pruning. The RHS reports few usual pest or disease problems. Grow new plants from seed in summer or autumn. Sow at temperatures of 6–12°C. You can also split off offsets while the parent corms rest. These are two ways to grow more plants for a collection.