Plants perennial; densely tufted, neither stoloniferous nor rhizomatous. Basal branching intravaginal. Culms 10-35 cm tall, erect or the bases decumbent; nodes terete, 0-1, exserted. Sheaths closed for 1/4-3/4 their length, terete; innovation blades 0.5-1.2 mm wide, involute, moderately thick, moderately firm, abaxial surfaces smooth of scabrous, adaxial surfaces usually densely scabrous or hispidulous; cauline blades usually gradually reduced distally, 0.5-1(-2) mm wide, flat, folded, or involute, thin, sometimes withering early, abaxial surfaces smooth or scabrous, apices narrowly prow-shaped; flag leaves sometimes vestigial. Synflorescences 2-8 cm long, erect, narrowly lanceoloid to void, contracted, congested; nodes with 1-2 branches; branches 0.5-3 cm long, terete to angled, scabrous. Spikelets 4-8 mm long, lengths to 3 times widths, broadly lanceolate to narrowly ovate, laterally compressed, not sexually dimorphic; florets 2-5; rachilla internodes 0.5-1.2 mm long, smooth or scabrous. Glumes lanceolate, shorter than the lowest lemmas; calluses glabrous; lemmas 4-7 mm long, lanceolate, distinctly keeled, puberulent, sometimes sortly villous, intercostal regions usually glabrous, infrequently softly puberulent proximally, lateral veins moderately prominent, margins glabrous, apices acute; paleal keels scabrous; anthers usually vestigial (0.1-0.2 mm long), rarely 2-3 mm long. 2n = unknown.
Poa x nematophylla is thought to bonsist of hybrids between Poa cusickii subsp. pallida and Poa fendleriana. It is mostly pistillate and apomictic but a few staminate plants have been found. It is usually more similar to Poa cusickii subsp. pallida but grades towards Poa fendleriana. It tends to grow on drier slopes than either parent mainly in and around sagebrush desert/forest interfaces.