Eriophorum vaginatum

Eriophorum vaginatum is a perennial, tussock-forming sedge. It has a cespitose (tufted) growth habit, with multiple flowering stems at the base of the plant. A stem may reach up to 60 cm (24 in) tall, with a persistent brown sheath at its base. Basal leaves are approximately 1 mm wide and noticeably shorter than the flowering stem. There are 1–3 leaves along the length of the stem, each reduced to a sheath (no leaf blade). The uppermost sheath is conspicuously inflated. The inflorescence is a single erect spikelet at the tip of the stem. The spikelet bears numerous florets, each covered by a scale (a type of bract in sedges and grasses). At the base of the inflorescence, there are 10 or more empty scales (with no flowers), the lowermost scales becoming spreading or reflexed at maturity. The flower parts emerge from the axils of the floral scales. After pollination, each floret develops 10 or more white bristles that elongate to 2 cm at maturity. The fruit is a small brown nutlet no more than 3.5 mm long.^[5][6][7]

For identification purposes, the cottongrasses divide into two groups based on the number of spikelets. Eriophorum vaginatum is a member of the unispicate group since it has one (not multiple) spikelets. It is similar in appearance to the unispicate species Eriophorum brachyantherum and Eriophorum callitrix. All three species have densely tufted stems (cespitose) and 10 or more empty scales at the base of the inflorescence. Eriophorum vaginatum is distinguished by having white-margined empty scales with the lowermost scales spreading or reflexed (not appressed to ascending), a conspicuously inflated sheath, and a tussock-forming growth habit.^[8]

Eriophorum vaginatum subsp. spissum is very similar to the typical subspecies described above, differing in a few characters only:^[9][10][11]

Subspecies spissum is a smaller plant with a more compact tussock. It occurs throughout northeastern North America but the full extent of its range is unknown.

Eriophorum vaginatum, the type species of genus Eriophorum,^[12] was first described by the Swedish botanist Carl Linnaeus in 1753.^[3] Linnaeus based his diagnosis on specimens with smooth sheathed culms collected in the cold, barren regions of Europe.^[13]

In 1926, the American botanist Merritt Lyndon Fernald named and described Eriophorum spissum as a segregate taxon of Eriophorum vaginatum in northeastern North America.^[14][15] In 1942, the Swedish botanist Oskar Eric Gunnar Hultén reduced Eriophorum spissum to a subspecies,^[16] and in 1967, the Canadian botanist Joseph Robert Bernard Boivin further reduced it to a variety.^[17] As of March 2026^[update], the name Eriophorum vaginatum subsp. spissum (Fernald) Hultén is accepted by some authorities,^[18][19][20] while others accept the name Eriophorum vaginatum var. spissum (Fernald) B.Boivin.^[21][22][23] Still others accept a broadly defined Eriophorum vaginatum L.^[1][4][24]

Hultén claimed that the two taxa were largely sympatric in Alaska and Yukon, and that the range of subspecies spissum extended westward at least as far as the Lena River in Siberia. He concluded that the distinction between the taxa was unclear at best.^[9][10][25] His work influenced Flora of North America to recognize a single taxon in 2002.^[5]

Fernald simultaneously published the names Eriophorum spissum and Eriophorum spissum var. erubescens in 1926.^[14][26][27] The latter was first described as Eriophorum callitrix var. erubescens by Fernald in 1905 based on a specimen collected in Newfoundland.^[28][29] The epithet erubescens, which means "turning red",^[30] refers to the color of the perianth bristles. In 1951, the Canadian botanist Louis-Florent-Marcel Raymond described a hybrid of Eriophorum russeolum and Eriophorum vaginatum subsp. spissum,^[31] placing Eriophorum spissum var. erubescens (Fernald) Fernald in synonymy with the hybrid name.^[32] In 1992, Boivin reduced Eriophorum spissum var. erubescens to a form of Eriophorum vaginatum var. spissum.^[33] He listed Raymond's hybrid name as a synonym of the new form.^[34] As of March 2026^[update], the accepted name of this taxon is Eriophorum × pylaieanum Raymond.^{[35][36][37][38]}

Eriophorum vaginatum occurs throughout the subarctic and temperate regions of the Northern Hemisphere. In Eurasia, its range extends from Spain in southwestern Europe to Japan in East Asia, northward to Siberia and Scandinavia.^[4] In North America, it occurs from Alaska south to British Columbia, east through the Great Lakes region to New England, and north through eastern Canada to Greenland.^[7] It prefers acidic, moist to wet, peaty soil and may be dominant in bogs, poor fens, and the heathlands of Western Europe. In the Arctic, it is commonly found in the peaty tundras of Russia and North America.^[45] It is common in Scotland where it is sometimes referred to as draw-ling or drawmoss.^[46][47]

In Merionethshire, Wales, seasonal growth of Eriophorum vaginatum begins around mid-March and continues until the end of November. In the southern Pennines in Northern England, it is in full fruit by June. Peak flowering occurs in May but flowering can occur in April or even as early as March. In the northern Pennines, there is a second flowering period during September and October.^[48]