Eriophorum angustifolium is native to the Northern Hemisphere, and distributed across Eurasia, North America and the British Isles, where there is open bog, heath, wetland and moorland, with standing water and calcareous peat or acidic soil. It can survive in the Subarctic and Arctic, and is found in Alaska, Finland and Greenland as far north as 83° N. The British botanist William Turner Thiselton-Dyer recorded E. angustifolium in the South African Republic in 1898.

In North America, Eriophorum angustifolium is found in the north from Alaska through Manitoba and the Canadian Prairies to Newfoundland and Labrador, down the Pacific Northwest and the state of Washington, across the Midwestern United States through Michigan and Iowa, down the Eastern Seaboard as far south-east as New York and New Jersey, and reaching as far south-west as New Mexico. 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. It grows throughout continental Europe, with the exception of those parts within the Mediterranean Basin, growing in Scandinavia in the north, and as far south as the Norte Region of Portugal and the Pierian Mountains of Greece.

Eriophorum angustifolium is the most common of the four native species of Eriophorum in the British Isles, and has been recorded as having existed in all vice-counties, thriving particularly well in Ireland and northern and western regions of Great Britain, but less so in southern and eastern areas. 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. In central and southern counties of England, the species is rare or absent, and was "completely destroyed" in Cambridgeshire, The Broads, The Fens and other parts of the East of England by human activities such as land reclamation. 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. It has an altitudinal limit of 1,100 metres (3,600 ft) above sea level, reaching 854 metres (2,802 ft) in the Wicklow Mountains of Ireland, and 1,060 metres (3,480 ft) in the Scottish Highlands.

Eriophorum angustifolium is a hardy, herbaceous, rhizomatous, perennial plant, 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. It grows vigorously from seed over a period of 2–5 years, and thrives particularly well in freshly disturbed, cut or eroded peat. E. angustifolium is protogynous.

Sexual reproduction in Eriophorum angustifolium begins with flowering in spring or early summer (in or around May), when groups of 3–5 brown flowers are produced. Fertilisation usually takes place in May or June, via anemophily (wind-pollination), 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. These pappi endure well into summer, lasting from around June to September. 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.

It is a known host to the fungal species Myriosclerotinia ciborium, Hysteronaevia advena, Lachnum imbecille and Lophodermium caricinum.

Eriophorum angustifolium has a NatureServe conservation status of G5, meaning that the species is considered to be ecologically secure by NatureServe, lacking any threats to its global abundance.

Eriophorum angustifolium seeds and stems are edible and are used in traditional Native American cuisine by Alaska Natives, Inuit and Inupiat people. The leaves and roots of E. angustifolium are also edible and, because of their astringent properties, used by the Yupik peoples for medicinal purposes, through a process of decoction, infusion or poultice, to treat ailments of the human gastrointestinal tract, and in the Old World for the treatment of diarrhoea. In abundance, E. angustifolium can grow with enough density to disguise wetland and bog. Consequently, it may be used as a natural indicator of areas which are hazardous and to avoid travelling through. Attempts to make a cotton-like thread from the hairs of the plant's seed-heads have been thwarted by its brittleness, but it has been used in the production of paper and candle wicks in Germany, and was used as a feather substitute in pillow stuffing in Sweden and Sussex, England. In Scotland, during World War I, it was used to dress wounds.

In 2002, the County Flowers campaign of Plantlife International, which asked members of the public to nominate and vote for a wildflower emblem for each of the counties and metropolitan areas of the United Kingdom, resulted in Eriophorum angustifolium being announced as the County Flower of Greater Manchester.

The species was named Eriophorum angustifolium in 1782 by the German botanist Gerhard August Honckeny. The German botanist Albrecht Wilhelm Roth published this name in 1788, referring to Honckeny's work, and is sometimes erroneously considered the author of the species name. The genus name Eriophorum consists of two Ancient Greek roots – εριων (erion, "wool") and -φόρος (-phoros, "-bearing") – referring to the fibrous seed-heads of the genus, which resemble tufts of thread. The specific epithet angustifolium is composed of the Latin words angustus ("narrow") and folium ("leaf"). The Linnaean name Eriophorum polystachion is a nomen rejiciendum, being based on a mixed batch of specimens. Scirpus angustifolius is a later combination published by the Japanese botanist Tetsuo Koyama in 1958, but this generic assignment is not widely accepted.

Two subspecies are recognised within E. angustifolium. The autonymous subspecies, E. angustifolium subsp. angustifolium, is found in more southerly sites, while E. angustifolium subsp. triste has an overlapping distribution centred further north. The two also differ in height and the roughness of the peduncles, with E. a. subsp. angustifolium being up to 100 cm (39 in) tall and having smooth-surfaced peduncles, while E. a. subsp. triste has rough peduncles and only reaches 30 cm (12 in) tall.

In English, E. angustifolium is known by a variety of common names (with various spellings), including common cottongrass, common cotton-grass, common cottonsedge, tassel cotton grass, many-headed cotton-grass, thin-scale cotton-grass, tall cotton-grass, downy ling and bog cotton.

Although "difficult to grow under cultivation", The Royal Horticultural Society states Eriophorum angustifolium can be cultivated as a low-maintenance wildflower, suitable for meadows, ponds margins or bog gardens. This may be done in sheltered or exposed terrain, but best accomplished with full sun at a south- or west-facing aspect, in water up to 5 centimetres (2.0 in) deep. Poorly-drained peat, sand, clay or loam with an acidic soil pH is required. Division in spring is the recommended form of propagation for the species, and regular deadheading is the recommended method of pruning. Narthecium ossifragum and Myrica gale are suitable for companion planting with E. angustifolium. Eriophorum angustifolium is "generally pest free". As a seedling and young plant it is eaten by sheep and cattle, and a variety of goose species. It is tolerant to chalybeate (iron-enriched) water, but may succumb to powdery mildews.

• Media related to Eriophorum angustifolium at Wikimedia Commons
• "Eriophorum angustifolium (Tall Cottongrass)". Minnesota Wildflowers. Retrieved 29 November 2024.