(spike trisetum)
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Photo of Trisetum spicatum by Carl Roland
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Trisetum spicatum is a tufted perennial grass that is very common, although rarely locally abundant, in a variety of habitats in Denali, occurring most frequently in the mountains (on both sides of the Alaska Range), but extending into the boreal zone along river corridors and bluffs. This species has narrow panicles with diagnostic hairy stems below the
inflorescence and long-
awned lemmas. Stems are 10-50 cm tall, growing from fibrous roots. Leaves are flat, 1.5-4 mm wide, with hairy, fringed
ligules. The
inflorescence is a compact
spike-like panicle 2-15 cm long, often purple to copper, or silvery in color.
Spikelets have 2 to 3 bisexual flowers.
Glumes are unequal in size but as long as or longer than the florets, 6-8 mm long.
Lemmas have two teeth at the apex and a distinct long bent
awn, 4-6 mm long. This gives the
inflorescence a slightly fuzzy look. This is the only member of the genus
Trisetum in the park. Another good trait to help identify this grass is the presence of the hairy stem below the tightly-packed flowering head with exserted
awns.
Trisetum spicatum typically flowers in mid-late summer.
T. spicatum is
monoecious and wind pollinated. Seeds are wind dispersed.
Trisetum spicatum is a widespread circumpolar species complex that has been split by some authors into various species and subspecies. In North America T. spicatum occurs from Alaska east across Canada to Labrador and south into the western U.S. states, New England and the mid-Atlantic states and even Mexico. In Alaska, this species occurs in suitable habitat statewide (most frequently in hills and mountains). In Denali this species occurs most commonly in the mountains on both sides of the Alaska Range, but extends in the adjacent lowlands along river systems and bluffs.
Details are shown in the Plots & Charts found at right, depicting recent Denali data.
T. spicatum is found in the park growing at elevations from 120 m to 1787 m with an average site elevation of 1066 m. This species slightly prefers south facing aspects. It prefers moderately steep slopes with an average slope angle of 17 degrees, although it is found in the park on a wide variety of slope angles (flat to 47 degrees).
Details are shown in the Plots & Charts found at right. For more on how to interpret these figures, visit Understanding Data Presented.
T. spicatum grows in well-drained sandy to rocky soils in alpine tundra, gravel bars, cliffs, lakeshores, open woods, and disturbed areas. Soil pH for sites where this species was found ranged from 4. to 7.8 with an average pH of 5.5.
Well-drained moist to dry sites.