Especially old fruit trees and other deciduous trees are often densely covered with lichens. Many gardeners suspect that these organisms are harming their trees. But is that really the case?
Do lichens damage fruit trees?
Lichens do not directly harm fruit trees because they live self-sufficiently and filter nutrients from the air. However, their presence can indicate weakened trees that may lack nutrients or are too dark. Improve the tree's conditions to promote its he alth.
What are lichens?
Lichens are not independent plants, but rather a community of fungi and algae. Both form a symbiosis in which they support each other. Fungi are able to extract water and nutrients from the soil or air, while algae produce nutrients using photosynthesis. In this way, the two organisms depend on and feed each other. There are around 2,000 different species that can have very different appearances, and the color spectrum also varies greatly. Lichens can lie loosely on their substrate, but some species are strongly attached to it.
Do lichens damage fruit trees?
Since lichens primarily grow on weakened and old trees, many gardeners suspect them of causing significant damage. This is not true because lichens feed self-sufficiently and do not rely on the fruit tree as a source of nutrition. They filter their nutrients from the air and not from the ducts of the infected tree. These organisms also do not hinder the growth of the bark; after all, due to the lack of roots, they do not penetrate into the Cambrian period - where the bark is formed. However, their presence is often a sign that the tree is not doing well: lichens prefer to colonize trees that are already weakened, as these no longer produce sufficient defensive substances. This is particularly true for trees that suffer from a nutrient deficiency or that are too dark.
When and how should lichen be removed?
It is therefore not necessary to fight the lichens. What you can do, however, is improve the conditions for your infested tree. This can be done by loosening the soil and fertilizing or by moving it to a sunnier location. If the tree is heavily overgrown with lichens and often struggles with recurring pest infestations, removal may still make sense: Some pathogens and pests like to hide in the organisms. However, the lichen can only be scraped off with vigorous scrubbing with a hard brush (€13.00 on Amazon) - chemical agents are not permitted for household use.
Tip
Lichens are considered indicator plants for he althy, clean air: Since the organisms have no excretory organs, they react very sensitively to pollutants from the air. So you can be happy if you find trees covered in lichens in your garden: This simply means that your air is literally clean.
