Stephen J. Darbyshire
Plants perennial; loosely cespitose. Culms 15-80 cm. Sheaths open nearly to the base; ligules membranous; blades rolled in the bud. Inflorescences open or closed panicles; branches often flexuous, capillary, spikelets distal. Spikelets usually with 2 florets, sometimes with additional distal rudimentary florets; rachillas not prolonged beyond the distal florets; first internodes about 0.5 mm; disarticulation above the glumes and beneath the florets. Glumes subequal to equal, equaling or exceeding the florets, membranous, acute to acuminate; lower glumes 1(3)-veined; upper glumes 3-veined; calluses obtuse, pilose, hairs about 1/2 as long as the lemmas; lemmas ovate, with 5(7) obscure veins, awned, awns attached near the middle of the lemmas, twisted, geniculate, visible between the glumes; paleas almost equal to the lemmas; lodicules 2, membranous, toothed or not toothed; anthers 3; ovaries glabrous. Caryopses adhering to the lemmas and paleas; hila linear to oblong, 1/4-1/2 the length of the caryopses. x = 7. Named for the Danish botanist Jens Laurentius Moestue Vahl (1796-1854), the son of botanist Martin Vahl.
Vahlodea is a monotypic genus with a discontinuous circumboreal distribution. It also grows in southern South America. The genus is sometimes included in Deschampsia, from which it differs in having loosely cespitose shoots and in lacking a rachilla prolongation beyond the distal floret.
1. Vahlodea atropurpurea (Wahlenb.) Fr. ex Hartm.
Mountain Hairgrass, Deschampsie Pourpre
Culms 15-80 cm, erect. Leaves glabrous or pilose; lower sheaths usually retrorsely hirsute, sometimes glabrous; uppermost sheaths glabrous or scabridulous; ligules 0.8-3.5 mm, rounded to truncate, often lacerate and ciliate; blades flat; blades of lower leaves to 30 cm long, 1-8.5 mm wide; blades of flag leaves 1-10 cm long, 1-5 mm wide. Panicles 3-20 cm; pedicels glabrous or scabrous-pubescent. Spikelets 4-7 mm. Glumes usually glabrous or scabrous on the keels and marginal veins; lower glumes 4-5(6.5) mm; upper glumes 4-5.5(7) mm; lemmas 1.8-3 mm, scabrous and ciliate apically, awns 2-4 mm; anthers 0.5-1.2 mm. Caryopses 1-1.5 mm. 2n = 14.
Vahlodea atropurpurea grows in moist to wet, open woods, forest edges, streamsides, snowbeds, and meadows, in montane to alpine and subarctic habitats. Plants from northwestern North America tend to have wider, more pubescent leaves and shorter lemma hairs than those elsewhere. They are sometimes treated as a distinct taxon, but the variation is continuous.