Fruit trees and other trees whose trunks and branches are covered with yellow, green, red or gray are particularly noticeable in late summer. Many gardeners remove the covering because they consider it harmful and fear that the tree will be damaged. But is that actually true?
Do lichens on trees damage trees?
Lichens on trees generally do not harm the trees because they feed themselves self-sufficiently via photosynthesis and do not take any nutrients from the tree. However, they are indicators of moist, shady locations that may be susceptible to harmful fungi.
What are lichens, mosses and algae?
The growth is particularly noticeable during the winter months, when the branches are free of leaves and therefore bare. Lichens, mosses and algae primarily grow in damp and dark locations, which is why older trees with a sprawling crown and corresponding shadows are affected.
Lichen
Lichens are not plants, but a symbiotic community of fungi and algae. There are an estimated 16,000 different species worldwide, all of which look very different in shape and color. However, lichens have one thing in common: they do not form roots that penetrate the bark of the tree. Lichens feed exclusively through photosynthesis and extract the moisture and nutrients they need from the air. This makes it clear that the tree itself is not being tapped. You can easily determine this yourself, because lichens only sit loosely on the surface and come off easily.
Moose
The mosses, which are very rich in shapes and species, are usually green, brownish or grayish in color. They are often found on the ground, for example in the lawn, but also on the bark of trees - where it is shady and damp. The wetter it is, the better the sometimes very dense carpets thrive. Moss reproduces very quickly via seeds, which are produced in large numbers in the seed pods.
Algae
Most people probably only know algae from the sea, but these plants are actually common on land too. There is often green algae on the bark of trees that cannot be seen with the naked eye - but still covers the tree. Some algae, such as the genus Trentepohlia, can be recognized by the strong, flat orange or red color of the bark. Algae also feel most comfortable where it is moist and shady.
Does the vegetation harm the trees?
In principle, growth with lichens, mosses or algae does not harm the trees because the epiphytes feed self-sufficiently on sunlight and air. However, increased growth must make one suspicious for other reasons, as it is a clear indication of a location that is too moist. Harmful fungi prefer to settle here and can actually cause major damage to the tree. However, this is not the fault of the lichens, because they are only an indicator.
How do you remove lichens, mosses and algae?
Basically, the growth doesn't need to be removed, you can just use a sponge and brush for aesthetic reasons. Mechanical removal is the only sensible option, but it is also very time-consuming.
Tip
Lichens occur primarily on deciduous trees. Mainly apple trees as well as poplars and ash trees are affected. However, the symbionts generally do not stop at any tree species.