Plants densely cespitose, without rhizomes. Culms (45) 60-100(120) cm, glabrous, smooth or scabrous below the inflorescence. Sheaths closed for less than 1/3 their length, smooth or scabrous, persistent; collars glabrous; ligules 2-5(9) mm, entire or lacerate, not ciliate; blades 1.5-3 mm wide, 0.8-1.8 mm in diameter when conduplicate, deciduous, abaxial surfaces scabrous, adaxial surfaces scabrous or pubescent, veins 9-15, ribs 7-13; abaxial sclerenchyma a more or less continuous band; adaxial sclerenchyma present; girders usually formed at the major veins, sometimes only pillars present. Inflorescences (7)10-15(17) cm, open, with 1-2(3) branches per node; branches 4.5-9 cm, lax, erect or spreading, spikelets borne towards the ends of the branches. Spikelets (8)10-14 mm, with (3)4-5(6) florets. Glumes unequal to subequal, ovate-lanceolate, scabrous or smooth, acute; lower glumes (2)3.5-5.5 mm; upper glumes (2.5)4.5-6.5(7) mm; lemmas 6-10 mm, lanceolate to ovate-lanceolate, scabrous or smooth, unawned, sometimes mucronate, mucros to 0.2 mm; paleas shorter than to as long as the lemmas, intercostal region puberulent distally; anthers 3-4.5 mm; ovary apices densely pubescent. 2n = 28, 42.
Colo., N.Mex., Utah, S.C., Ariz., Wyo.
Festuca thurberi is a large bunchgrass of dry, rocky slopes and hills, open forests, and meadows in montane and subalpine regions, at (1000)2000-3500 m. Its range extends from southern Wyoming south through Utah and Colorado to New Mexico.