Eriophorum angustifolium is a hardy, herbaceous, rhizomatous, perennial sedge, able to endure in a variety of environments in the temperate, subarctic and arctic regions of Earth.

[3][7] Up to seven green and brown aerial peduncles and chaffs, roughly 4–10 millimetres (0.16–0.39 in) in size, protrude from umbels at the top of the stem from which achenes are produced after fertilisation, each with a single pappus; these combine to form a distinctive white perianth around 5 centimetres (2.0 in) long.

[3][8] Eriophorum angustifolium is described as "a rather dull plant" in winter and spring,[9] but "simply breathtaking" in summer and autumn,[10] when 1–7 conspicuous inflorescences – composed of hundreds of white pappi comparable to cotton,[11] hair,[4] tassels,[9] and/or bristles[3] – stand out against naturally drab surroundings.

[8] Eriophorum angustifolium is native to the Northern Hemisphere, and distributed across Eurasia, North America and the British Isles,[3] where there is open bog, heath, wetland and moorland, with standing water and calcareous peat or acidic soil.

[7] It can survive in the Subarctic and Arctic, and is found in Alaska, Finland and Greenland as far north as 83° N.[12][13] The British botanist William Turner Thiselton-Dyer recorded E. angustifolium in the South African Republic in 1898.

[1][15][16] In Eurasia, E. angustifolium is distributed throughout the Caucasus, European Russia and North Asia, including Siberia and the Kamchatka Peninsula, and south-east to Manchuria and Korea.

[3][12] In the mires of Northern Ireland and the South Pennines, it considered a ruderal, pioneer and keystone species, because it can quickly colonise and repair damaged or eroded peat, encourage the re-vegetation of its surroundings, and retain sediment and its landscape to serve as a carbon sink.

[7][18] Within the British Isles, E. angustifolium thrives at a range of altitudes from sea-level fens and lowland meadows, to exposed upland moors when provided with a habitat of acid bog or waterlogged heath.

[14] Eriophorum angustifolium is a hardy, herbaceous, rhizomatous, perennial plant,[14] meaning that it is resilient to cold and freezing climatic conditions, dies back at the end of its growing season, has creeping rootstalks, and lives for over two years.

[3][11] Fertilisation usually takes place in May or June, via anemophily (wind-pollination),[20] and the white bristle-like perianth, composed of achenes with pappi (seeds with hairs) then grows outwards to appear like short tufts of cotton thread.

[3] Like the pappus of Taraxacum (dandelions), this aids in wind-dispersal, and also serves as thermal insulation, conserving the temperature of the plant's reproductive organs by trapping solar radiation.

[25] The leaves and roots of E. angustifolium are also edible and, because of their astringent properties,[15] used by the Yupik peoples for medicinal purposes, through a process of decoction, infusion or poultice, to treat ailments of the human gastrointestinal tract,[26] and in the Old World for the treatment of diarrhoea.

[7][27] Attempts to make a cotton-like thread from the hairs of the plant's seed-heads have been thwarted by its brittleness,[27][28] but it has been used in the production of paper and candle wicks in Germany,[20][29] and was used as a feather substitute in pillow stuffing in Sweden[29] and Sussex, England.