Does moss really grow on only one side of the tree?

Question

Does moss really grow on only one side of the tree?

Answer 1

Somebody else please report shasta as spam...

With regard to the question, it's not a universal phenomenon. According to Wikipedia:

"In northern latitudes, the north side of trees and rocks will generally have more moss on average than other sides (though south-side outcroppings are not unknown). This is assumed to be because of the lack of sufficient water for reproduction on the sun-facing side of trees. South of the equator the reverse is true. In deep forests where sunlight does not penetrate, mosses grow equally well on all sides of the tree trunk."

Answer 2

They say it USUALLY grows on the north side of the tree because it gets the least amount of sun and is the coolest so that it can grow better.  But it is not a hard and fast rule.

Answer 3

Usually, but not always.  The reason is that moss is a very delicate plant that is greatly affected by changes in temperature and sunlight.  Most plants are diploids and have seeds.  Moss is a haploid and has spores.  Spores need moisture to survive because they have thin walls and lack a substantial coating that would help them to retain water.  Sunlight is a natural enemy of moss because it dries up the moisture that the moss spores need to survive.    

Moss is like mold and algae in that it does not do well in direct sunlight.  In warm sunny climes (think Arizona and New Mexico) moss is difficult to find anywhere.   On the other hand, in cool moist areas (think the Pacific Northwest) moss is plentiful, and not just on the north sides.  Because the weather remains so  cloudy, moss can grow on all sides.  In a four-seasons climate (think Colorado) moss will usually only be found on the north because the high rate of sunshine prevents moisture from forming on the other three sides.  

[A good example of an "opposite" plant that has thick walls that safeguards its water inside, and is impervious to sunshine, is the Saguaro cactus that thrives in the hot southwest desert sun.]