Photo © Peter Lesica
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Trichophorum alpinum (L.) Pers.

Hudson's Bay Bulrush; Alpine Bulrush

Cyperaceae (Sedge family)

Synonym: Scirpus hudsonianus (Michx.) Fern.

General Description: Hudson's Bay Bulrush is a glabrous, grass-like perennial with clustered, 3-sided stems, 10-40 cm tall, and arising from a short rhizome. Culms bear several scale-like leaves and sometimes more fully developed sheathing and narrow leaves clustered near the base that are 5-12 mm long. The solitary, terminal, multi-flowered spike is 5-7 mm long and subtended by a long-tipped scale. Each flower consists of a single brown scale narrowed to a broad, blunt tip subtending three stamens and an ovary with six white bristles that greatly surpass the scale. These bristles form a silky tuft that extends 1-2 cm beyond the spikelet at maturity. The brown, three-sided achene is about 1.5 mm long and has a short beak.

Photo © Robert Bursik
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Illustration.

Field Identification Tips: The combination of a solitary inflorescence with tufts of long white bristles and 3-sided stems helps distinguish this species.

Phenology: Fruit matures in July-August.

Similar Species: The solitary inflorescence and tuft of long white bristles make this species resemble a slender Eriophorum, but it does not have at least 10 bristles per achene. It differs from the other species of Scirpus with solitary inflorescences by having bristles that are longer than the scale and a three-sided stem. Without the long bristles, S. hudsonianus would closely resemble Eleocharis pauciflora.

Habitat: Sphagnum bogs and fens, and other cold, wet places in the montane and subalpine zones.

Global Distribution: Circumboreal, extending south in North America to Connecticut, Michigan, Wisconsin, Saskatchewan, southern British Columbia, northwestern Montana, and northern Idaho.

Idaho Distribution: The Selkirk Mountains in Boundary County.

References:

Bursik, R. J. 1992. Field investigations of sensitive plant taxa occurring on the Priest Lake Ranger District, Kanisku National Forest, Idaho Panhandle National Forests. Unpublished report prepared for the Panhandle National Forests by the Idaho Department of Fish and Game, Conservation Data Center, Boise. 141 pp. plus appendices.

Montana Natural Heritage Program. Montana rare plant field guide. Available at: http://nhp.nris.state.mt.us.