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Lichens latch on to unhealthy plants
The Coast Gardener Newspaper and Web Column - June 23, 2001

Some call it a fungus. Others aren't sure what to call it. Everyone wants to get rid of it. What are those grayish green growths that occasionally show up on your plants? They are called lichens.

It is natural to become concerned when you see these growths appear on your shrubs. Fortunately, however, they do not cause any direct damage to plants. You do see them, however, on plants that are growing poorly. Even though they may appear to cause a problem, they are simply benefiting from an underlying cause of distress to your plant.So, what actually are lichens? They are composed of at least two plants growing together. One "plant" is a fungus and the other is an alga. The green algal part makes food for both of them. The fungal part helps keep both of them moist and healthy. Lichens do appear as a single growth and not as two plants growing in harmony with each other.Like other plants, lichens manufacture their own food supply. You have probably seen them growing on trunks and branches of trees and shrubs, but have you noticed them growing on soil and rocks, too? Because they do not need a host plant to survive, they can thrive on soil and rocks.Lichens vary in color and texture. They can be white, gray, green and yellow. Sometimes they look like leaves; other times they appear as tufts of hair suspended from branches. Lichens thrive almost anywhere. They grow in the subarctic regions of the world where caribou and reindeer eat them. Snails and insects use them as a food source, too. There are even accounts that Washington's troops at Valley Forge used them as a soup thickener!Plants that are slow growing or poor in health seem to be perfect targets for lichens. This may be because the branches are not increasing in size and shedding bark fast enough to shed the lichens. The lichens become more noticeable. This gives the impression that the lichens are causing the problem.

It is important to realize that lichens indicate that the plants are not as healthy as they could be. The affected plants may simply need to be placed on a proper fertilization program based on the results of a soil sample analysis. Another possibility is the soil may stay too wet or too dry for the plants in question. In addition, growth slows in mature plants. It is not uncommon to see lichens covering camellias, Japanese magnolias, hollies and other mature plants.

Remember that lichens could be a "red flag" to alert you that something could be wrong or they could just be a sign of old age. If you do have a problem, identify and correct it. Not only will you see a definite improvement in your plant's performance, but you will also notice fewer lichens.

These archived gardening columns were written by Chance McDavid, former Harrison County Extension Agent.