Feb 16 2011
Snow cover is increasingly hard to find in Pittsburgh so this scene is fading fast.
Exposed here by the melting snow is a plant whose name I’ve just learned: common haircap moss (Polytrichum commune).
I’ve often seen it in the woods where it covers the ground like a dense carpet of green bottlebrushes. Though it’s a moss, it’s rather tolerant of dry conditions and does well in a variety of Pennsylvania locations. I’ve read that in dry weather the green leaves wrap around the stem to protect the plant from moisture loss.
Its scientific name describes the plant well. Polytrichum means “many hairs.” Commune probably refers to its ability to form dense colonies.
Where are the hairs? I know we can’t see them in this photo because they’re so small. The hairs are on the caps that initially cover the brown spore capsules. The spore capsules are those brown heads on the naked brown stems poking out of the snow. So, yes, those brown stems are not a different plant. They’re the sporophytes of the haircap moss.
At this time of year the haircaps may be missing because they pop off to expose the spores for dispersal.
I’ve never seen any of this because I haven’t looked closely at this moss before. I didn’t even know that the brown stems are part of the moss’ life cycle.
Now that I know what to look for, I’m going to find those hairy caps. I wonder what time of year they’re visible…
(photo by Dianne Machesney)