Lichens are comprised of a fungus and alga living in a mutualistic or symbiotic relationship. The fungi portion acts as a housing mechanism for the alga to live and helps prevent it from drying out. The algal portion, often a cyanobacteria (blue-green algae), can photosynthesize and live on its own.
The fungus survives on the nutrients produced by the alga, and some believe that it is parasitizing the algal host. The fungus is what allows the algae to survive in barren or extreme environments including Antarctica.
Lichens can grow on trees, rocks, fences, and other wooden structures. They are often seen growing in colonies or groups and range in color from gray/green to bright orange or red.
Lichens will grow in three different forms. The first form is called crustose, pictured here, and will appear almost painted on the surface of the bark. It will be almost impossible to pry it loose.Foliose lichens will have more of a folded and/or leafy appearance. These are large and easy to observe in many habitats.
Lastly are the fruticose lichens and are more three-dimensional and appear quite different from the typical lichen species. For more information, visit the National Park Service website to see multiple variants of these.
Simple facts: lichens cover about 8% of terrestrial earth and contribute nitrogen and other nutrients to the ecosystem in which they live. Lichens can also absorb some pollutants, however they will not be found in the presence of sulfur dioxide as they are very sensitive.
Lichens can be an indicator of air quality to some degree. There are also some that believe in their usefulness in forest navigation. It is said that lichen and moss are more likely to grow on the north side of a tree, allowing them to help with directional travel for those who are lost, but in truth, they grow on all sides.
And now for the big question, will they hurt the tree? The answer is no. They can however be an indicator of a slower growth pattern or declining tree as they do not grow well on vigorously growing trees.
Their presence does seem to be more prevalent without explanation. Some of that could be due to weather conditions and wet rainy patterns.
Because they cause no negative effects, there is no management strategy required. In fact, attempts to physically remove them may cause damage. Identification and understanding of what they are will help you determine a course of action, if any.
One more fun fact: there are some insects that have adapted to living in the environment with lichens and appear as though they are harmless lichens to their prey or from being preyed upon. Examples of these insects include the giant lichen orbweaver, the grizzled mantid, and green leuconycta.
Please don’t hesitate to reach out to the Ewing Technical Services Team with any questions or with future topic ideas.