Mat muhly is a graminoid with culms that are 30-60cm tall, wiry, nodulose-roughened, and erect or decument at the base. It has a narrow panicle that is interrupted, or sometimes rather close and spikelike, 2-10cm long, spikelets are 2-3mm long and in a contracted (vs open) panicle. Glumes are ovate and about half as long as spikelets. Lemmas are lanceolate, acute, mucronate, awnless and glabrous on the back (vs minutely pubescent). Ligule is 2-3mm long, blades are usually involute, 1-5cm long, rarely longer.
Its lemmas, which are awnless and glabrous on the back (vs minutely pubescent), and its spikelets, which are in a contracted (vs. open) panicle are distinguishing characteristics.