Yellow-Flag Iris Seeds (Iris pseudacorus)

Yellow-Flag Iris (Iris pseudacorus) is a tall native perennial of marshes, ditches, flood plains and pond margins, growing 100 to 150cm tall. It forms dense clumps of stiff, grey-green, sword-shaped leaves from thick creeping rhizomes, and carries branching stems of large, buttery yellow flowers with three drooping outer petals from May to August, followed by fat green seed pods.

Bumblebees are the main pollinators, pushing into the large flowers for nectar, and hoverflies and other insects also visit. The dense leafy clumps give cover and nesting habitat for waterfowl, amphibians and invertebrates at the water’s edge. It is long-lived and robust once settled.

This is strictly a plant for wet ground. It needs permanently moist or waterlogged soil, in full sun or partial shade, and will grow in shallow water at a pond edge, along a ditch, in a marsh or on a river bank, tolerating seasonal flooding. It is vigorous and spreads by rhizome and by floating seed, so it can dominate a small pond; give it room, or confine it in a basket in a garden pond, and keep it out of watercourses where spread is unwanted.

Sow in autumn or spring onto bare, wet soil at the water’s edge, pressed firmly into the mud and lightly covered. Germination can be slow and uneven, and plants take two to three years to flower. Cut back dead foliage in late winter and divide clumps every few years if they outgrow their space. Combine with our wetland and pond-edge mixes or single species that share the same permanently damp conditions.