Hesperantha coccinea aka River Lily

Hesperantha coccinea is a flowering perennial in the iris family. Its names include crimson flag lily and scarlet river lily. An older scientific name is Schizostylis coccinea. Its native range runs from eastern Zimbabwe to South Africa’s Eastern Cape. In the wild, it grows beside streams and in wet ground. It spreads by rhizomes rather than corms.

The plant forms clumps of upright, grass-like green leaves. These grow from the base and have smooth edges. Leaves reach about 1.5 feet (0.46 m) long. They can stay green through mild winters. NC State gives a height of 1–2 feet (0.3–0.6 m). The RHS gives a taller range of 1.6–3.3 feet (0.5–1 m). Clumps spread to about 1.6 feet (0.5 m) wide. They grow fast, reaching full size in two to five years.

Scarlet flowers open from August to October on upright spikes. Each spike holds four to fourteen cup-shaped blooms with six petals. The RHS gives a flower width of about 1.6 inches. NC State reports larger blooms, about 2.5 inches wide. The flower spikes reach about 2 feet (0.6 m) tall. They draw butterflies and provide late colour in borders. The blooms also last well as cut flowers.

Give this plant full sun, though it accepts light shade. It needs soil that stays moist while it grows. Loam and sandy loam suit it, but it accepts other soils. It grows in acid, neutral, or alkaline ground. The RHS favours good drainage, while NC State notes tolerance of wet soil. Keep plants out of cold, drying winds. Add mulch in winter to help protect the rhizomes. The listed hardiness ranges are USDA zones 7–9 and RHS H4. Plants may struggle in hot, humid southern summers.

Use it in sunny beds, meadow plantings, or small garden spaces. It also suits pots, rain gardens, and gardens planned for butterflies. Divide clumps in spring to make more plants. Remove spent blooms to help extend the flowering season. Cut the stems down once flowering ends. Both the RHS and NC State report few pest or disease problems. Even so, NC State and Missouri Botanical Garden rate its maintenance needs as high.