Molinia caerulea is an herbaceous perennial bunchgrass (tussock-forming), growing up to 90 cm (35 in) tall (taller when sheltered bygorse and heather), with many closely packed stems. The leaves are coarse, green, taper to a point, long, flat and sometimes slightly hairy on top Due to the dense tussock it is very resistant to heath fires. Its ligule is a ring of hairs, as in heath grass (Danthonia decumbens). The long narrow purple spikelets are a major identification feature - the panicle is 15 cm (6 in) long.
It flowers between July and September, later than any other species.