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GRASSES OF THE COLUMBIA BASIN OF BRITISH COLUMBIA Heather Stewart, Richard Hebda Major Groups of Grasses Table of Contents Glossary Aira Hairgrasses Hairgrasses originated from Europe where there are nine species. They are generally delicate annuals with extremely fine leaves. They have little forage value and are not considered troublesome. In British Columbia there are two species, Aira caryophyllea and Aira praecox. Only Aira caryophyllea has been collected in the Columbia Basin region.   Aira caryophyllea L. Silver Hairgrass Plant: Aira caryophyllea is an introduced species that grows to 5-30 cm tall. It is a tufted annual with an open, widely branched flowerhead. Leaves and Stem: The sheaths are open and the leaf blades are extremely narrow 0.3-0.7 mm, occuring mostly at the base of the stem. The ligule is 1.5-3.5 mm long, slightly hairy and has a tattered tip. There are no auricles. Flowerhead and Flowers: The broad and diffuse flowerhead is 2-6 cm long, with tiny shiny, silvery spikelets at the ends of the thin branches. The two glumes are equal, 3 mm long and enclose two flowers. The lemmas are 2-2.5 mm long and bear bent, twisted awns that are 2.5-3.5 mm long and attached below the midpoint. Habitat: Silver Hairgrass grows in dry, open rocky sites and sometimes invades rock gardens. In the Columbia Basin it grows at Hamilin Lake. Similar Species: Early Hairgrass (Aira praecox) is very similar to Silver Hairgrass, but has not been collected in the Columbia Basin. The two are easily distinguished by the different flowerheads. The flowerhead on Silver Hairgrass is open and widely branched, compared to a tightly closed flowerhead of Early Hairgrass. In addition, Silver hairgrass has shorter lemmas than Early Hairgrass. Annual Bluegrass (Poa annua) is another small-tufted annual grass like Silver Hairgrass, but Silver Hairgrass does not have folded leaves and does not root at the nodes like Annual Bluegrass.

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