Monday, June 1, 2015

Lichens and Moss on Trees

Should I remove the moss and lichens growth that are growing on the trunk of my tree?

The light to dark greenish growth growing on the limbs and trunks of trees can either be moss or lichens. Lichens is a bit odd in that it is actually two different organisms, a fungus and an alga living together. It is the fungus that provides the shape with the algal cells growing in a layer near the top of the fungal structure. The algae manufacture food, a process called photosynthesis, for both the fungus and the algae: a symbiotic relationship.The lichen structure is usually grayish-green in color, paper-like, and forms small circular to irregular-shapes.

Lichen and moss are frequently seen growing on twigs and branches, especially under moist conditions. When wet from rain or dew, they are active growers but when dry, they stop growing. They do not die but lie dormant until the next rain starts.

 They are both considered harmless.  Although these organisms attach themselves to the tree, they are not pulling vital nutrients from that tree. It is often thought that lichens and moss are injuring a tree because they are growing so well and the tree is declining. There is a relationship between the vigorous growing moss/lichens and the decline of the tree, but not the way most people think. The trees are growing poorly not because of the moss or lichens, rather just the opposite. Trees decline first, shedding leaves and thus allowing more light to penetrate to the bark of the trunk and limbs. This, in turn, will cause a new growth spurt in the moss or lichens. This growth spurt is an indication that some other requirements of the plant are not being met. Check and make sure there is no insect infestations (scale, aphids), no old weed- whacker damage and make sure the tree is adequately fertilized. 

If you are troubled with this type of growth on your trees, take heart in the fact that most lichens will not grow in a smoky or polluted atmosphere.