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Trichophorum pumilum (Vahl.) Schinz & Thellung

Rolland's bulrush; Dwarf bulrush; Small clubrush

Cyperaceae (Sedge family)

Synonyms: Scirpus rollandii Fern.; Scirpus pumilus Vahl.; Scirpus pumilus Vahl. ssp. rollandii (Fern.) Raymond; Trichophorum rollandii (Fern.) Hultn.

General Description: A glabrous, grass-like perennial with loosely tufted, slender stems 5-12 cm tall and arising from slender rhizomes clothed in the remains of dead culms and persistent leaf bases. The leaves have slender blades 5-15 mm long and up to 1 mm broad above, but consist only of shorter sheaths near the base. The inflorescence is a small, solitary spikelet of 3-6 flowers borne on the stem tip and subtended by a brown, blunt-tipped bract. Each flower consists of a brown scale with thin, whitish margins subtending 3 stamens and an ovary with 3 stigmas. The scales fall off as the ovaries mature into smooth, blackish achenes (fruits) 1-2 mm long.

Illustration.

Field Identification Tips: Rolland's bulrush can be recognized by its small, loosely tufted, slender, stems, small leaves, and minute, solitary, terminal spikelet. After the achenes mature plants look like a tiny stick with a few tiny black eggs glued on top. Rolland's bulrush is an inconspicuous plant easy overlooked in its graminoid-dominated habitat.

Photo K. Moseley
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Phenology: Flowers July, August and early September.

Similar Species: Most Scirpus species in Idaho have more than one flowering spike, as well as one or more elongated bracts below the inflorescence. However, two species have small, solitary, terminal spikelets similar to Rolland's bulrush. Scirpus caespitosus is a larger plant that forms distinctive tussocks and in Idaho appears to be restricted to peatland habitats. Scirpus hudsonianus has triangular stems and conspicuous, elongated perianth bristles. In comparison, Rolland's bulrush has more rounded stems and no perianth bristles. Eleocharis species (spike-rushes) have solitary, terminal spikelets and can also look similar. They can be distinguished by lacking leave blades and technical differences in the flower such as thickened style bases which appear as a cap-like feature on the achenes. Kobresia simpliciuscula has multiple terminal spikelets and is commonly taller and more leafy than Rolland's bulrush.

Habitat: Rich fens; wet calcareous soils. Associated species at Idaho populations include Eleocharis pauciflora, Kobresia simpliciuscula, Deschampsia cespitosa, Triglochin maritima, and Primula alcalina.

Global Distribution: Circumboreal; in North America extending from the Yukon to Quebec and southward to Montana, Idaho, Wyoming, Colorado, and in California.

Idaho Distribution: Known from the upper Little Lost River Valley in Custer County, and Birch Creek in Clark County.

References:

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

Spackman, S., B. Jennings, J. Coles, C. Dawson, M. Minton, A. Kratz, and C. Spurrier. 1997. Colorado rare plant field guide. Bureau of Land Management, Lakewood, CO, and other cooperators.

Wyoming Rare Plant Technical Committee. 1994. Wyoming rare plant field guide. USDI Bureau of Land Management; National Park Service; Fish and Wildlife Service; USDA Forest Service, Intermountain Region and Rocky Mountain Region; Wyoming Game and Fish Department; and The Nature Conservancy, Wyoming Natural Diversity Database.