Calamagrostis canescens aka Purple Small Reed

Calamagrostis canescens, or purple small-reed, is a long-lived perennial grass. It belongs to the grass family, Poaceae. Its native range spans Europe, Siberia and Türkiye. The RHS lists it as native to Britain and Ireland. In the wild, it grows in marshes and other wet sites. These include salt marshes, where it can form broad stands.

This grass forms loose clumps and grows at a fast rate. Garden plants reach 3–5 feet [0.91–1.52 metres] tall. Their spread is 2–3 feet [0.61–0.91 metres]. Shallow rhizomes let the clumps spread fast beyond their starting point. The slender green stems have no side branches. Flat green leaves give the plant a fine texture. Each blade narrows to a point and has smooth edges. Small hairs make the leaf surface feel rough. A ligule may show where the leaf meets the stem. The leaves keep their shape well through winter. Their later colours include brown, copper and tan.

The flowers form an open, branched panicle with an oblong outline. Each head sits above the leaves and nods a little. Fine hairs give the flower heads a soft look. Purple flowers appear in late summer, with the display extending into fall. As the season moves on, the heads turn tan. Their colour and form give the grass its main floral interest. The fruit is a caryopsis, a grain with its outer wall attached. The seed heads remain part of the fall display.

Grow this grass in full sun for its preferred light conditions. It also accepts some shade during the day. It suits moist to wet soil with good drainage. The listed soils include clay, loam and sand with added organic matter. Acid soil suits it, and its USDA hardiness range is 4–9. It needs little routine care and can be grown from seed or division. Its wet-site needs suit pond edges, stream banks and bog gardens. Plantings can also help limit soil erosion. Deer resistance adds to its value in these settings.

Few major pest or disease problems are reported for this grass. Even so, aphids, spider mites, mealybugs and grubs may occur. Rust, leaf spot and crown rot are also possible. Its fast rhizome growth merits thought when choosing a planting site. A loose clump can become a wider patch over time.