The culms of this perennial sedge are solitary or tufted; they are
1½–4' tall at maturity. The culms are light to medium
green, terete, hairless, and unbranched. Several alternate leaves
occur along the entire length of each culm; they are ascending,
arching, or floppy. Individual leaf blades are 2–12" long and 1.5–5 mm.
across; they are medium green or yellowish green, linear in
shape, hairless, and rough-textured along their margins from
minute teeth. The leaf blades are usually flat toward their bases, but
they become furrowed toward their tips. Each fertile culm terminates in
a dense cluster of several spikelets. Each spikelet is about 6–10 mm.
long, consisting of a head of overlapping scales and their florets.
Individual scales are 4–5 mm. long and ovate in shape with about 5
longitudinal nerves; young scales are green, but they later become
Each floret consists of a single stamen and an ovary with a tripartite
style; 6 or more hair-like bristles originate from the
base of the ovary, providing the spikelet with a hairy appearance.
Depending on the stage of development, these bristles are reddish brown
to light brown (rarely all white); they become longer as the spikelets
mature. The peduncles of the spikelets are short (about 2–8 mm. in
length). Directly underneath the cluster of spikelets, there are 2–5
spreading leafy bracts of variable length (½–6"). The blooming period
occurs from mid-summer to late summer,
lasting 2-4 weeks for a colony of plants. The florets are
cross-pollinated by the wind. Afterwards, the hair-like bristles of the
spikelets become twice as long, extending to about 12-20 mm. in length.
Mature achenes are 2.5–4 mm. long, oblongoid-ellipsoid in shape,
somewhat 3-angled, and brown to black. The hair-like bristles of the
achenes help to distribute them by wind or water. The root system is
fibrous and rhizomatous. Clonal offsets are occasionally produced from
the rhizomes. Sometimes colonies of plants develop at favorable sites.
The preference is full or partial sun, wet to consistently moist
conditions, an acidic soil with abundant organic matter, and cool
weather. This perennial plant is very winter-hardy.
Habitat: Tawny Cotton Grass (Eriophorum virginicum)
is rare and
state-listed as 'endangered' in Illinois, occurring in only 2 counties
in the NE section of the state, where it is native (see Distribution
Map). Tawny Cotton Grass is widely distributed in NE USA, the
Lakes region, adjacent areas of Canada, and along the Appalachian
Mountains. Illinois lies along the southwestern range-limit of this
species. Habitats consist primarily of shrubby bogs, where there has
been some accumulation of peat. In Illinois, this is a very
conservative species that is found only in high quality natural areas.
It is more common in boreal areas further to the north where bogs are
aphid that was introduced
from Europe, Ceruraphis
eriophori, feeds on the sap of cotton grasses
during the summer (Blackman & Eastop, 2013). A
widely distributed seed bug, Cymus
discors, has been found in the
seedheads of cotton grass; it is known to feed on the seeds of bulrushes
and other sedges. In boreal areas, the caterpillars of a butterfly,
Oeneis jutta (Jutta
Arctic), feed on these plants (Bug Guide at
www.bugguide.net, accessed 2017). The foliage of cotton grasses is
eaten by a variety of mammalian herbivores, including such domesticated
animals as cattle and sheep, and such wild animals as the American
Moose, White-tailed Deer, American Bear, and Canada Goose (Innes, 2014;
Romain et al., 2013; Morris, 2014). In northern boreal areas of Canada,
the diet of Tree Sparrows (Spizella
arborea) consists primarily of the seeds of cotton
grasses and sedges (Carex
spp.); see West (1973). It is likely that
other birds also feed on the seeds of cotton grasses.
A shrubby bog in Lake County, Illinois.
its common name, Tawny Cotton Grass (Eriophorum virginicum)
a sedge, not a grass. It is easily distinguished from other cotton
grasses (Eriophorum spp.)
by the brownish hairs of its seedheads and
the relatively late time of year that they develop (typically during
late summer). In contrast, other cotton grasses develop their seedheads
during late spring or early summer, and the hairs of their seedheads
are white. Tawny Cotton Grass can also be distinguished by the solitary
stamens of its florets and the multiple veins on the scales of its
seedheads. Other cotton grasses in Illinois have florets with three
stamens and single-veined scales. As a group, cotton grasses are very
ornamental because of the hairs on their seedheads, but they have more
stringent requirements for cultivation than most plants.