LICHENS ON PLANTS INDICATE POOR PLANT GROWTH, by Larry Williams UF/IFAS Extension Agent

Lichen001Lichen growing on this crepe myrtle tree indicates poor plant growth. Correctly identifying and correcting the causes will allow the tree’s health to improve, and lichens will gradually disappear.

Do you have trees or shrubs with trunks and branches covered with gray-green crusty growths?

These growths–called lichens–are harmless and do not cause plants’ poor growth or decline.

Lichen is an alga and a fungus growing together in a symbiotic relationship. The alga supplies the fungus with carbohydrates through photosynthesis; the fungus protects the alga from drying. Lichens are not pathogens, nor are they parasitic to plants. They simply need something to structurally support them.

As a tree or shrub declines in health, the canopy thins, allowing more light to penetrate the plant. The additional light and the plant’s slow growth allow lichens a better environment to grow.

When lichen growth is abundant on dying limbs and branches, ask, “Why is the plant growing poorly?” Diagnosing the problem may be difficult, requiring considerable plant knowledge.

Reasons for a plant’s poor health range from incorrect plant placement or poor growing conditions to injuries from mowing equipment and misplaced lawn chemicals. Trees and shrubs planted too deep will usually be in a state of poor health. The plant may be declining from lack of fertilizer or because the pH is incorrect. Or, it may be due to an older plant’s natural decline.

Correctly identifying and correcting the causes for poor growth will allow the plant’s health to improve, and lichens will gradually disappear.

Your local University of Florida/Institute of Food and Agricultural Sciences Extension Office can assist with identifying the possible causes for poor plant growth.

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