Racomitrium lanuginosum is most commonly found on exposed rock surfaces and boulders. Patches of this species can also be seen growing with Racomitrium elongatum on gravel on the roof of the UBC Biological Sciences Building.
In the photo to the left, R. lanuginosum is growing in a bog.
Racomitrium lanuginosum is an acrocarpous moss that grows in hoary grayish-green to whitish-green mats.
Shoots are irregulary-pinnately branched. The conspicuous, whitish awns are rather flexuouse when dry.
A cross-section of the distal part of a leaf reveals that sharp papillae are confined to the hyaline marginal areas which correspond to the decurrent strips of the awn. Also note that the lamina is wholly unistratose while the costa is bistratose.
The costa extends beyond the leaf apex into the awn.
The hyaline awn is decurrent, with sharp papillae and large, multicellular teeth.
The seta is twisted near the base of the sporangium. It moves hygroscopically to aid with spore dispersal.