Numerous older trees, not only in the garden and in green areas, are densely overgrown with lichens. In the following article we will clarify why these settle and whether this is harmful to the tree. You will also find out if you need to do anything to protect the tree against this collective of fungi and algae.

Lichens indicate good air quality

How are lichens formed?

Lichens are among the longest-lived creatures on earth. They can be several hundred years old, in exceptional cases even over a thousand years old. Strictly speaking, these growths are not plants, but a community of algae and fungi.

The fungus that forms the body of the lichen, which absorbs water and minerals from the environment, cannot carry out photosynthesis on its own. However, the alga, which cannot absorb moisture or nutrients itself, is able to do this and produces sugars that are essential for life during this process. The fungus also protects the algae from drying out and mechanical damage.

Causes of lichen growth

Tree lichens, of which 25,000 species are known, often occur on the bark of deciduous trees and some fruit trees. They need similar living conditions as mosses and prefer shady places with high humidity.

Lichens depend on good air quality and are therefore considered indicator plants for pollutants in the air. For this reason, trees with heavy lichen growth are rarely found on busy roads and in urban areas.

Are lichens damaging the tree?

  • Since they do not penetrate the interior of the wood, lichens are not harmful.
  • They are not an indication that an old tree is in poor condition.
  • Thanks to the symbiotic properties, they provide themselves with water and nutrients.
  • They only settle on the tree bark, which is even protected from other fungi and bacteria.
  • Lichens provide shelter for numerous useful small animals.

When should lichen be removed?

This is only necessary as trunk care on older fruit trees as the protective lichens offer shelter to overwintering pests. The right time for this measure are the cold winter months. The lichens are brushed off with a special tree brush, which you can get in garden shops. Please do not use a wire brush as this would permanently damage the bark of the tree.

tips

Tree lichen can also be removed with a coat of lime. First scrape off the lichen and loose bark parts and then apply the preparation. The lichens die within a few weeks because they are deprived of their livelihood. At the same time, the coating prevents fungal diseases and prevents frost cracks.

Category:

Trees