Feb 16 2011

Haircap Moss

Published by at 7:00 am under Winter Weeds & Trees


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)

2 responses so far

2 Responses to “Haircap Moss”

  1. Marcy Con 17 Feb 2011 at 8:23 am

    When I was out for my walk on Tuesday, I saw these poking up thru the snow…looks like the same photo…when I was a teenager, I used to sit on this moss and play my guitar in the white pines we had where I grew up…very soft rug…

    During my walk, I also saw some other wild flowers greening up….corydilis, chickweed, and glad the deer didn’t find it yet, downy rattlesnake plantain, (an orchid)….willow trees are turning a yellow cast….signs that spring is closer…but we still have some snow, even after yesterdays warmer temp in the high 40s. Best part now, if we get snow, it doesn’t last forever…the sun is warmer and melts it…

  2. Veronicaon 23 Feb 2011 at 5:17 pm

    This is one of the things I love about your blog. All these plants I’ve seen in the woods since childhood, always wondering what they were and struggling to find good resources to look it up. Then I look at your blog and here it is! ;)

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