Lichen

Filed Under:
March 12, 2013
This time of year I get calls about this moldy stuff growing on plants, and whether it will harm the tree and shrubs. The cause for concern is an organism called lichen. Lichen are very interesting and are found throughout the southeast and beyond. A misconception many gardeners have is that lichen are parasites, feeding on the landscape plants. Actually the lichen is only growing the surface of the bark. They are composed of an unlikely combination of a fungus and algae that are combined in a symbiotic relationship. In other words the algae and fungus have taken a “likin” to each other. There are three main types of lichen that are commonly seen on our landscape trees. Some spread on the tree, very flattened in appearance. These are the crustose forms of lichen, and like the name suggests, may look a little crusty. Other lichens develop folds that resemble a crumpled sheet as they spread across a branch. These wavy folds are produced by folicose forms of lichen. The third commonly found forms of lichen are organisms that are highly branched with multiple projections. These projections can have a very fine texture that resembles little balls of hair growing on a limb. These are the fruiticose forms of lichen. Lichens are commonly observed on trees and shrubs that are struggling; for example, this live oak with the circling roots. In reality, the lichens were already present before any decline started, giving the illusion of causing the problem. Now I personally think that lichen adds a touch of patina to our landscape plants. I’m horticulturist Gary Bachman for Southern Gardening.

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