Lichens and the Health of Your Trees & Plants

Published 7:00 am Wednesday, April 18, 2018

Dr.Eddie Smith

In their natural habitat, lichens are a beautiful part of the landscape. However, when they invade trees and shrubbery, homeowners frequently become concerned about the health of their plants. In most instances there is no real reason for concern, since lichens do not directly cause injury to landscape plants. Lichens are unique creatures in the plant world. While they are considered to be one plant, they are actually made up of a fungus and an algae living in association with one another. However, the appearance is that of a single plant.

Lichens manufacture their own food and grow on soil, on rocks, and trunks and branches of trees and shrubs.

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They occur in several forms such as crusty gray, green, yellow, or white growths. Some are leaf-like, others resemble a tuft of horse hair hanging from branches.

Lichens are amazing creatures for other reasons as well. They frequently serve as a source of food for snails, mites, and insects. In subarctic regions, lichens are a food source for reindeer and caribou. In hard times, lichens have served as a source of food for man, such as when Washington’s troops at Valley Forge used lichens as a soup thickener.

Most often lichens appear on plants that for some reason are in a poor or declining condition. Why lichens tend to “pick-out” weak plants as preferred colonization sites is not entirely understood.

But for whatever reason, such plants often support profuse lichen growth, and it’s easy to understand why home landscapers think the lichens are responsible for poor plant growth.

It’s important to realize that lichens do not cause the plant to grow poorly, but they may indicate that something is wrong.

So when your azalea, camellias, plum or apple trees, or other landscape plants are affected by these oddities of the plant kingdom, remember it’s not the lichens that are the problem.

It could be an entirely normal occurrence, since lichens also occur on healthy plants, or a signal that your plant has something else affecting it.

If you need assistance in identifying problems in the home landscape, give us a call at your county Extension office.