It’s not unusual to find lichens growing on trees and sometimes the greyish-green crust can be quite attractive. But you may be concerned that this fungus could cause serious damage to your trees. The good news is that it’s completely harmless and, as you’ll discover, a fascinating organism.
What are lichens?
Lichens are the result of a symbiotic relationship between fungus and algae. The fungus is unable to photosynthesise which means it cannot produce its own food. And the algae cannot retain moisture which it needs to survive. So the two organisms form a partnership with the fungus capturing moisture for the algae, and the algae making food for the fungus.
How do lichens affect trees?
As any tree care specialist will tell you, lichen will not cause any damage to your trees. They do not use trees as a source of food – only as a place to grow. They do have roots which they use to attach to the bark of a tree, but the roots don’t go deep enough to cause any harm.
That’s partly why lichens are rarely found on young trees. As young trees grow, they shed their bark too quickly for it to take hold. And while lichens may be more commonly found on older, diseased or dying trees, they’re not the reason for the tree’s poor condition. Lichens require sunlight to grow, and trees with thinning crowns provide them with the right conditions to thrive.
Do lichens provide any benefits?
Most lichens are sensitive to air pollution and can be used to gauge the air quality in a specific area. They also act like a sponge, soaking up water and then slowly releasing it back into the environment. In forests, this helps to regulate the humidity as the water doesn’t run off or evaporate as quickly.
They also provide shelter for smaller insects, which in turn provides food for birds. You may notice that birds tend to favour trees covered in lichen for this very reason.
Over long periods of time, lichens also contribute to soil production; releasing acids which dissolve rock and freeing minerals which enrich the soil.
In the past, lichens were used to dye wool and scent soaps and perfumes. Today, lichen is still used to make litmus paper.
How to remove lichen from trees
There’s really no need to remove this harmless organism from your trees, but if you’d prefer to get rid of lichen, there are some solutions. You could simply scrub the bark of your trees with a soapy solution. As the roots are not that firmly attached you won’t have any trouble getting the lichen off. But take care not to scrub too vigorously or you risk damaging the bark.
You could also try a commercial fungicide or a spray made with copper sulphate. Make sure you follow the instructions on the bottle and avoid the roots and leaves of the tree when applying the solution.
Finally, you could discourage the lichen from growing by changing the environment. Lichens grow in cool, partly sunny and moist conditions. By thinning your trees to let in more light and moving your sprinkler system away from the area, you’ll make it harder for the lichen to thrive. Ensuring that your trees are in good health will also discourage lichen from taking hold.
The next time you spot a grey crust spreading over the bark of your trees—don’t panic. Lichen is a generally a good sign and won’t have any effect on the health of your trees. If you’re still not sure, get in touch with Brands Tree Felling and our horticulturist will be happy to come out and assess the health of your trees.