Are Lichen Harmful To Your Trees?

What comes to mind when you hear the word lichen? Perhaps a plant or some sort of algae? A fungus, or a moss? Actually, lichens are combinations of green algae and fungal tissue. Each lichen specie is one alga species plus one fungus. The alga, a microscopic green plant, makes the food for the duo, while the fungus, a non-green plant, gives the pair support and soaks up moisture.

This cooperative arrangement benefits both creatures and the surrounding system, but raises a frequently asked question…

Are lichens harmful to your trees?

No. Those grayish-green patches, usually one to three inches in diameter, are not feeding on your trees. Since lichens are able to make their own food with moisture and sunlight, they have no need to parasitize other plants. Lichens grow on the surface of your tree, and do not penetrate any tissue. Instead, they make use of the trunk or branches for support. They do not cause plant diseases either, with one exception: in certain wet, tropical areas, lichens have grown in such thick layers over trees that their shade alone has caused leaves to die.

Believe it or not, lichens are often viewed as making a tree more picturesque. Most people don’t mind having lichens on their tree’s bark. They can add color, contrast, texture, and natural beauty to your landscape. Lichens play a very significant role in our biological world. For one, they act as air pollution indicators. Although a lichen is able to withstand harsh conditions, such as freezing, thawing, high light and heat intensities, when an area is polluted, lichens will become scarce and eventually stop growing. Lichens also help regulate the composition of gases in the earth’s atmosphere. Each creature acts as a sponge to catch and store excess gases, one of which is carbon dioxide. In essence, lichens help filter the air we breathe. Some lichen also have the ability to return valuable nitrogen to the soil. These are three significant roles lichens have been found to play; however, as research continues, more are sure to be uncovered. Who knows what will come to mind the next time you hear the word lichen?

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