Old Man's Beard

The is actually a lichen called “Usnea,” which is the name of several species of lichen that grow hanging from tree branches, resembling greenish gray hair. It is commonly called Old Man’s Beard, beard lichen or tree moss. 

 

Does the lichen kill the trees, or do they prefer dead or dying trees? 

 

Because they do seem to prefer trees or shrubs already beginning to die, the lichen is often unjustly blamed for adversely affecting the tree. In actuality, many lichens grow rapidly when exposed to full sunlight, and that is why they are a common occurrence on dead or dying trees. Their position on the trees gives them a secure location to anchor as well as access to sunlight in dark forests. When the tree whose canopy is failing eventually dies, the lichen’s growth greatly increases because of the additional sunlight. This is why many dead or dying trees are often covered with lichens. Dying trees also often release a kind of sugar or sap, a lure for lichen – but lichens do not consume any part of the plant, nor do they poison it.