Sidewalk mosses crack me up.

July 31, 2006

These two sunny mosses can be found all over North America in the cracks of sidewalks and asphalt paving:

Bryum Caespiticium, pronounced "Bri-um sespeeteesee-um", is called the "green sidewalk moss" and

Bryum argenteum, pronounced "Bri-um argentee-um", goes by the common name the "silver sidewalk moss".

Both are in the genus Bryum and both can take full sun, if need be. They are both used extensively as bonsai moss. Also many gardeners desire these mosses for the cracks in their garden pathways. I dont know of any place you can buy them but they are very common. I could find B. caespiticium in downtown Chicago in five minutes and B. argenteum in ten minutes. But as hot as it has been lately they can be hard to recognize in their dehydrated state. Last year I helped my bryology mentor at a bioblitz in Busey Woods in Champaign, Illinois. We took a break from walking through the woods and Mac said "letÂs not forget to inventory the sidewalk mosses. LetÂs go out to the parking lot, IÂm sure weÂll find them there." Last year was dryer than this year and almost as hot. We split up in the parking lot and after five minutes I went over to Mac and said " ThereÂs no moss in this parking lot". He proceeded to pick up small sand crusted pieces of detritus and identify both B. caespiticium and B. argenteum. Up close B. argenteum has a pretty blue green cast to it.

On my photobucket album I have two pixs, one labeled Bryum caespiticium which is a fully hydrated growing example and the other pix is Bryum Caespiticium2 which has three sods of B. caespiticium. Click on the second pix to enlarge the photo. In this second pix the sod on the left which is dry in this picture grows in full sun four to six hours per day and has received water whenever it rains, and the rains have been adequate this summer. I keep this sod and others like it on sand on a clay saucer which has drainage holes in it. The sod on the right is from a plastic tray that sits also outside but in the shade on the north side of my porch. It gets no direct light but bright indirect light. This sod sits on plastic which never drains unless I remember to tip the tray after a big rain. The moss gets drenched but is never under water or completely water logged. This sod is growing very rapidly. I suspect the darker color of the sod on the left is the moss reacting to the bright light.

And the third sod in the middle is B. caespiticium as I found it today on a sidewalk at the base of the Dollar General building brick wall in downtown Galesburg, Illinois where this moss gets full sun eight or more hours per day. Because of its location this sod only gets water infrequently. This moss sod is dry and does not appear to be alive but I had broken off a piece of this sod and watered it and it came to life in a few minutes.

Notice how the two dried moss sods have sand grains showing. This is because the tiny moss leaves have closed up against the tiny stems and you can clearly see the sand but not really much of the moss leaves while the moss is dehydrated. The moss on the right also has sand but you cannot see the sand in the sod because the moss leaves are fully hydrated and widespread.

At my home I also have Bryum caespiticium growing on black dirt at the base of a tree on the treeÂs north side. This moss is more "fluffy" with the moss leaves even more widespread and the moss taller. Sometimes even the simplest of mosses display much differently under different environmental conditions making you think that you have different species. These two mosses are examples of sunny mosses that are easy to propagate and under the right conditions they will grow and expand rapidly.


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