Eriophorum virginicum, the tawny cottongrass, is a species of flowering plant in the sedge family Cyperaceae. It is native to eastern North America but was introduced in British Columbia in western Canada. It is most common in eastern Canada, New England, and the Great Lakes region. It is the only species of Eriophorum in North America that occurs in the southeastern United States, where it is uncommon. The common name refers to the tawny color of its fruiting head. Despite the name, it is a sedge, not a grass, and it is sometimes called tawny cottonsedge to emphasize this fact.
Eriophorum virginicum is a perennial herbaceous plant that forms colonies by means of long-creeping rhizomes. Each stem (or culm) in the colony grows up to long. The terminal inflorescence comprises 2–10 spikelets, each on a peduncle between 2 and 10 mm long. The inflorescence is subtended by 2–5 leaf-like bracts, the longest of which is in length. Individual flowers have 10 or more perianth bristles that are brown in color (at least at the base). Rarely the bristles are entirely white.
Typically the fruiting head is densely packed, which tends to obscure the spikelets. Despite this, Eriophorum virginicum is rather easy to distinguish from other cottongrasses due to its late fruiting time and distinctive color.
Eriophorum virginicum was first described by the Swedish botanist Carl Linnaeus in 1753. Linnaeus based his diagnosis on a specimen collected in Virginia, hence the specific epithet virginicum and the common name Virginia cottongrass.
Eriophorum virginicum was segregated to a new genus Eriophoropsis by the Austrian botanist and mycologist Eduard Palla in 1896. Later, in 1958, it was segregated to the existing genus Scirpus by the Japanese botanist and collector Tetsuo Michael Koyama., both Eriophoropsis virginica and Scirpus virginicus are considered to be synonyms for Eriophorum virginicum
Eriophorum virginicum var. album was described by the American botanist Asa Gray in 1876. Variety album has white (not brown) bristles. In 1924, the American botanist Karl McKay Wiegand reduced the variety to forma. Both names are considered to be synonyms for Eriophorum virginicum
Eriophorum virginicum is native to eastern North America, from Newfoundland and Labrador in Canada to South Carolina in the United States (U.S.), ranging as far west as Minnesota. It was introduced in British Columbia in western Canada. In the U.S., it is most common in New England and the Great Lakes region. It is the only species of Eriophorum in North America that occurs in the southeastern U.S., where it is least common.
Eriophorum virginicum is an obligate wetland (OBL) species. In New England, it prefers bogs, acidic fens, and wet meadows.
Eriophorum virginicum is a perennial flowering plant that flowers in the early summer. After the flowers are pollinated, cotton-like fruiting heads develop during mid-summer and early autumn. In Minnesota, fruiting occurs from July to September.