Plants perennial; cespitose, not mat-forming. Culms 5–15 cm, erect. Ligules 1–2.5 mm, acute to obtuse, entire; blades 2–8 mm wide, flat or folded. Panicles 2–4 cm, usually con-tracted and dense, sometimes slightly diffuse at maturity, lowest node usually with long and short branches, lower branches erect to ascending, spikelets usually confined to the distal 2/3; pedicels glabrous and smooth, lacking tumid epidermal cells or with very small tumid epidermal cells. Spikelets 3.8–6.5 mm, with 2–4(5) florets. Glumesbroadly ovate, enfolding the bases of the lower lemmas, rounded over the back, veins obscure or distinct, apices acute to obtuse; lower glumes 2–3.5 mm, at least 2/3 as long as the adjacent lemmas; upper glumes2.4–4 mm; rachilla internodes abruptly broadened at the point of attachment to the lemmas, less than 0.09 mm thick; calluses with a few hairs; lemmas 3–5.2 mm, usually herbaceous and mostly purplish, sometimes mem-branous with purple veins, basal 1/2 hairy over and between the veins, backs rounded, 5-veined, veins obscure or distinct, often dark purple, not extending to the margins, apical margins hyaline, often yellowish, smooth, apices acute, entire, becoming erose with age; palea veins with curly, intertwined hairs on the proximal portion, scabrous distally; anthers 0.8–1.5 mm. 2n = 14.
Puccinellia vahliana is an arctic species that is circumpolar, except in the Beringian region. In the Floraregion, it extends from Alaska through northern Canada to Greenland. It is generally non-halophytic, growing in calcareous gravel, sand, clay, or moss of imperfectly drained moist areas, and on seepage slopes from near sea level to 700 m, or, rarely, in seasonally dry, turfy sites. It is often a pioneering species in moist clay and silt by alpine brooks, ephemeral lakes, glacial runoff streams, and on snowbeds. The roots of this species and P. wrightii are characteristically thicker and more tightly curled than those of other Puccinellia species. It sometimes hybridizes with Phippsia algida.