Anyone who has walked in the woods has seen areas of rock or soil covered with a thick, green carpet. Moss has few features that call it to our attention, but it is an old and venerable life form unique to most plants you find in the forest.
The low, green moss common in our area is sometimes called cushion or carpet moss. It is one of the true mosses under a plant class called Musci. Moss is very different from other plants in that it has no true roots that take in water and nutrients from the soil. It has only structures called “rhizoids” that serve to anchor the moss in place. Water is absorbed throughout the plant surface, and it has the ability to store a good deal of water for dry times and for reproduction. Part of the life cycle of mosses is that reproductive cells “swim” to join other individuals of their species, rather like the animal world.
A clump of moss is actually a group of small individual plants, each made up of spongy stems covered with small green leaf-like structures. Moss has no true flowers, but sends up a golden thread-like structure with a spore capsule on the end that releases spores to grow new moss plants.
Moss prefers moist, shady locations, but can be found on dry ridges and slopes. It prefers acidic conditions, and can be used as an indicator of acid soil. You can find it in pasture fields that badly need lime. Since it doesn’t need soil for water or nutrients, moss can grow on solid rock. Mosses are often the first plants to colonize exposed rocky areas, and help break down rock by the freezing of water retained by the plant and by the actions of secreted chemicals. On logs they delay water loss, speeding up the growth of decay organisms. Mosses also serve as cover for insects and can be found as a building material in some bird’s nests.
Moss is an ancient species, having been around far longer than flowering plants. Fossil records indicate they existed over two and one half million years ago. So the next time you see some moss growing in the woods, maybe it deserves closer look.
Steve Roark is the Area Forester in Tazewell, Tenn. for the Tennessee Department of Agriculture, Forestry Division.