Eriophorum angustifolium aka Common Cotton Grass

Eriophorum angustifolium is a perennial sedge known as cotton grass. It belongs to the sedge family, Cyperaceae. Its native range spans the northern hemisphere's cool and temperate regions. These include parts of Europe, Asia, and North America. It is native to Britain and Ireland. In the wild, it grows in peat bogs and marshes. It also grows in acid meadows and wet ground beside water.

This evergreen plant forms tufts that spread through roots and seeds. Garden plants reach about 1–1.6 feet [0.3–0.5 metres] tall. Some sites produce plants 2–3 feet [0.6–0.9 metres] tall. Mature clumps can spread 3.3–4.9 feet [1–1.5 metres] wide. Plants reach full size within two to five years. The narrow, dark green leaves grow along angular green stems. Leaves reach about 1.3 feet [0.4 metres] long. They are flat, hairless, and set in an alternate pattern.

Clusters of flower spikes rise above the leafy stems. Each flower has a brown to purple scale at its base. The heads start oval, then widen as fine tassels develop. Their white hairs give the plant its cotton-like look. RHS places this display in summer. Chicago Botanic Garden lists bloom from July through October. NC State also records spring and summer flowers. The tiny brown seeds have three sides in cross-section. Wind carries mature seeds away, helping the plant spread.

Grow cotton grass in full sun and acid soil. It accepts some shade, but needs a wet site. Clay, loam, and sand can all support it. It also grows well in peat-rich ground with poor drainage. Plant it beside ponds or in shallow standing water. RHS allows water up to about 0.16 feet [0.05 metres] deep. It suits water gardens, rain gardens, containers, and small groups. Sources give USDA zones 4–7 and 4–8, plus UK rating H7. Growth is fast, and roots can spread beyond their space. Remove seed heads before ripening to limit seedlings. Divide plants in spring; regular division can also curb root spread. Pests cause few problems, though powdery mildew may occur.

PFAF lists roots and young stem bases as edible. Both may be eaten raw or cooked after suitable preparation. Remove the dark outer covering from roots. NC State lists the seeds as inedible. PFAF reports no known hazards, but this does not establish safety. Past uses include leaves and roots for diarrhoea. Seed hairs supplied stuffing, paper, tinder, and candle wicks. Their brittle fibres made them poor substitutes for cotton. People also wove dried leaves and stems into mats.