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Wisconsin Plant of the Week

Eriophorum viridi-carinatum (Engelm.) Fernald

Cyperaceae (Sedge Family)

Common Name:

tall cottongrass

06/05/2000

Wisconsin has eight species of cottongrass (Eriophorum). All are native perennials with conspicuous cottony heads or spikelets and they grow in bogs. Tall Cottongrass and a very similar species, Narrow-leaf Cottongrass (E. angustifolium), are also found in fens and in open areas of conifer swamps.

Cottongrasses are not true grasses but members of the sedge family. Sedges superficially resemble the grasses, since they have narrow leaves and inconspicuous flowers without showy petals.  Unlike the grasses, which have hollow stems, the stems of most sedges are solid.  Grass flowers each have two tiny scales, while sedge flowers have only one.

Each of the cottongrass spikelets contains many small flowers and each flower has many straight bristles.  The bristles extend beyond the rest of the flower parts and elongate as the seeds form and mature.

Tall Cottongrass grows to about 0.6 m and flowers in May and June. Each stem has several drooping spikelets and 2 or more leafy green bracts that extend beyond the cluster of spikelets.  The similar Narrow-leaf Cottongrass is distinguished by a band of dark red at the base of the cluster of spikelets and at the top of each leaf sheath where the leaf blade joins the stem.  Tall Cottongrass has no red.

  • Origin of the name: Eriophorum: Gr., erio, wool; Gr., pherein, to bear or carry; viridi-carinatum: L., viridis, fresh green; L., carinatus, keeled.  Refers to the prominent mid-nerve on the scales.
  • Range: Nf. to BC, s. to CT, MN, WA 
  • WI Range:  Most common north of the Tension Zone
  • Common associates: Tamarack, white cedar, pitcher plant
  • Wetland Indicator Status: OBL
  • Coefficient of Conservatism: C = 10 (S&W), C = 8 (MI)
     
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