Many gardeners do not like to see lichens that thrive on the wood of ornamental trees such as lilacs, for aesthetic reasons alone. They also fear that the heavy lichen infestation will have a long-term negative impact on the vitality of the tree.
Does lichen infestation harm lilacs?
Since the lichen only uses the wood as a base for its own growth, the lichen infestation hasno consequencesfor theplant he alth. On the contrary: the lichen growth even protects the lilac from environmental influences and the penetration of pathogens or fungi.
What are lichens?
Lichens are not plants that grow into the tree, buta collective of algae and fungi. The two organisms enter into a symbiosis:
- The fungus absorbs water from the environment, which the algae is unable to do.
- The alga performs photosynthesis, which the fungus cannot.
The fungus forms the body of the lichen and is responsible for its white, yellow, orange, brown or green color. It covers the algae and protects it from drying out.
Should I remove the lichen from the lilac?
Since lichens do not grow into the wood of the lilac and do not remove nutrients from the tree,theydo not need to be removed. However, on older lilac trees, lichen growth can cover the buds and prevent leaves and flowers from developing.
In this case, it may make sense to remove the lichens on the trees with a soft brush. However, this should be done with caution, as the lichens also provide some protection for the bark.
Tip
Lichens are indicator plants for air quality
Because lichens absorb water and nutrients from the air, they rely on a clean environment. They are very sensitive to air pollution and are considered indicators of air quality. That's why you rarely find lichen growth on city trees, while the bearded lichen, for example, can grow up to a meter long in the clean air of many Alpine regions.
