Eriophorum L., commonly known as cottongrasses or cotton-sedges, is a genus of perennial herbaceous plants in the sedge family Cyperaceae (order Poales). Established by Carl Linnaeus in 1753 in Species Plantarum, the genus currently comprises around 16–27 accepted species (depending on the authority consulted), distributed across cool temperate, alpine, and Arctic regions of the Northern Hemisphere.
Plants are rhizomatous perennials with single or tufted culms (stems) arising from basal and cauline leaves whose blades range from filiform to flat, up to 25 cm long. The defining character of the genus is the perianth: each flower bears 10 or more smooth, hair-like bristles that elongate dramatically at fruit maturity to form the dense, white or tawny cottony heads that give the plants their common name. These bristle tufts facilitate wind dispersal of the achenes. Flowers are wind-pollinated and plants are monoecious; each spikelet produces trigonous achenes with three-parted styles.
Species typically grow in bogs, fens, acid meadows, and alpine tundra — consistently wet, often acidic substrates. In Arctic environments, the dense bristle heads serve an additional thermal function, trapping solar radiation to warm the reproductive organs and extend the brief growing season. Plants reach approximately 60 cm in height and spread by rhizomes to form extensive stands, which are ecologically significant components of northern peatland systems.
Etymology
The genus name Eriophorum is derived from Greek: erion ("wool") and phoros ("bearing"), meaning "wool-bearer." The name directly references the conspicuous cottony tufts formed by the elongated perianth bristles at fruit maturity — the same feature responsible for the English common name "cottongrass."
Distribution
Cottongrasses are primarily plants of the Northern Hemisphere, concentrated in cool temperate, alpine, and Arctic zones. Records indicate around 14 species in Asia, 11 in North America, and 8 in Europe. In North America, species occur across the northeastern United States, adjacent Canada, and scattered sites in the Midwest and Southwest, consistently in wetland habitats. In Europe, five species are documented in Switzerland alone (E. angustifolium, E. gracile, E. latifolium, E. scheuchzeri, E. vaginatum), reflecting a broader European distribution that extends through Scandinavia, the British Isles, and into northern Asia and Siberia. The overall range also reaches Greenland.
Ecology
Eriophorum species are obligate wetland plants, characteristic of bogs, fens, acid meadows, pond margins, and alpine tundra. They grow in moist to wet, typically acidic soils ranging from light to heavy clay, and tolerate full sun to semi-shade. In the Northern Hemisphere's peatland systems, cottongrasses are among the most ecologically significant vascular plants, structuring habitat and contributing organic matter to peat accumulation. An adaptation specific to Arctic populations is the ability of the white bristle tufts to act as passive solar collectors, trapping radiation and elevating temperatures around the developing fruits — an advantage in environments with short, cool growing seasons. The genus is hardy to roughly USDA zones 4–8.
Uses
Cottongrasses have been used by northern peoples across multiple continents. The long, silky seed-hair bristles were employed as filling for pillows and bedding, and as wicks for oil lamps and candles. They were also processed into paper and experimentally tested as a cotton substitute, though the fibers proved more brittle than true cotton (Gossypium). Dried leaves and stems were woven into baskets and mats. Medicinally, the astringent leaves and roots were used to treat diarrhea, and some Native American groups consumed raw stems as a general restorative. Roots can be eaten raw or cooked after removing the dark outer covering; young stem bases are also edible.
Propagation
Eriophorum can be propagated by seed or vegetative division. Seeds should be sown in spring into constantly moist, slightly shaded conditions; germination typically occurs within 2–6 weeks at around 15 °C. Division of established clumps is described as very easy and can be carried out in spring or autumn, with divisions replanted directly into wet or boggy soil. The genus requires consistently wet, acid substrates and will not thrive in dry garden conditions.
Taxonomy
Eriophorum was established by Carl Linnaeus in 1753 with four species in Species Plantarum (Sp. Pl.: 52), with a fifth added in 1762. The genus is placed in the family Cyperaceae, order Poales, class Liliopsida. As of 2025, Plants of the World Online (POWO) accepts 16 species and 8 natural hybrids, while World Flora Online recognizes the same set with the exception of Eriophorum arcticum. GBIF (usageKey 2730118) lists 27 accepted taxa, with 56 total descendant taxa once synonyms and infraspecific entities are included. The number of recognized taxa has remained broadly stable since 1994.
