Lichens & Trees

— Written By and last updated by Nancie Mandeville
en Español

El inglés es el idioma de control de esta página. En la medida en que haya algún conflicto entre la traducción al inglés y la traducción, el inglés prevalece.

Al hacer clic en el enlace de traducción se activa un servicio de traducción gratuito para convertir la página al español. Al igual que con cualquier traducción por Internet, la conversión no es sensible al contexto y puede que no traduzca el texto en su significado original. NC State Extension no garantiza la exactitud del texto traducido. Por favor, tenga en cuenta que algunas aplicaciones y/o servicios pueden no funcionar como se espera cuando se traducen.

English is the controlling language of this page. To the extent there is any conflict between the English text and the translation, English controls.

Clicking on the translation link activates a free translation service to convert the page to Spanish. As with any Internet translation, the conversion is not context-sensitive and may not translate the text to its original meaning. NC State Extension does not guarantee the accuracy of the translated text. Please note that some applications and/or services may not function as expected when translated.

Collapse ▲

Lichens are non-parasitic organisms that grow on rocks, gravestones, and woody plants, without causing any harm to them. They can have beautiful shapes and colors. If you take the time to look at them closely and study them, you will discover that they can have leaf-like or crust-like structures and may be attached loosely, very tightly, or even embedded. Homeowners often become concerned when they see large amounts of these growing on trees. They are worried that the lichen is affecting the health of the tree.

A lichen is a symbiotic relationship between two different organisms, a fungus, and an alga, where each contributes something in support of the other. The fungus is the dominant partner, providing the lichen it shape and fruiting bodies. The alga can be a green alga or a blue-green alga. These algae are both known as cyanobacteria and many lichens will have both types. The fungus does not contain chlorophyll or other means of producing its own food, so it relies on other organisms for nutrition. This is where the alga comes in. Because the alga can photosynthesize, it contributes sugars, starches, and other nutrients to the fungus and in return, the fungus collects water and minerals from the air and shares them with the alga.

When you see lichen growing on trees, it may be because the canopy is thin for some other reason, such as disease or insects, or abiotic stress from drought, compacted soil, or flooding. The Urban Forester in my office believes you see lichens growing on trees that are not thriving, again meaning the tree may be stressed in some way. Lichen prefers sunny areas with good air circulation, so plants with thin canopies provide excellent growing conditions. Consider that lichen could be an indicator to you that your tree is stressed and you should investigate to determine if there is a problem and then take steps to correct it if possible.