The second-most abundant moss in Denali, this feather moss grows in large mats, found from forests to the alpine. Plants are a yellow to green color. Shoots are 5-10 cm tall. The branches are irregularly pinnate. The leaves are concave, ovate and blunt-tipped, loosely overlapping and covering the red stem. Plants can initially look similar to stair-step moss (Hylocomium splendens) but stems lack the red paraphyllia, and stair-step growth pattern found in that species. Big red stem also has a characteristic sheen when dry, while stair-step moss appears dull.
Rarely fertile, plants mainly reproduce vegetatively through lateral branching and fragmentation.