Growing healthy, strong trees can be challenging for someone who is not a professional but takes it seriously.  You have changes in seasons which can bring about its own set of challenges, but bugs, disease, rodents, pesticides, fungicides, lack of water, soil acidity and a host of other issues can create a hostile environment for a tree.

We can certainly see how hiring a local tree service to take care of your trees would be appealing, especially when you start to notice things that could resemble bacterial/fungus.  When you see white spots on your trees then you immediately think that something is wrong, but not all growths are entirely bad.

If you begin to notice a set of white spots, or “marks” on your trees then it’s likely that you have Lichens growing on them.  In the past, Lichens were thought to be pests or a disease, but that is not so.  Lichens are a non-parasitic plant-like organism that are naturally occurring on trees, rocks, shrubs and other areas of nature.  Though they look like they are taking over a tree, they are absolutely harmless and do not penetrate the outer bark of a tree.

Although Lichens are technically a fungus, it is also made up of an alga where both live together creating a symbiotic relationship.  Because the fungus lacks chlorophyll, it lacks the ability to create its own food, but it can use up the carbohydrates produced by its resident algae.  So what does the algae get in return?  Well, it gets a structure, or home, where it can reside.  In this structure it gets a steady supply of water and nutrition that it receives from its surrounding atmosphere.  This symbiotic relationship is analogous to the bird that

What are lichens?

As previously mentioned, Lichens are actually two organisms living in harmony with each other.  It is made up of fungus and algae, that when living together, each actually benefits from the other.  But why would they want to live off each other?  Fungi lack the green pigment known as chlorophyll and therefore do not have the ability to convert sunlight into carbohydrates for energy and nourishment.  As a result, they need to seek out external sources of food.  In this case, it’s mutually beneficial for them to co-exist with green algae who can utilize photosynthesis as a form of constant nourishment.  In exchange, the fungi provide a structured, protected environment that shields them from the sun’s damaging ultraviolet rays.  It is extremely common for fungi to form a protective shell with pigments that absorb harmful and deadly ultraviolet rays that can kill algae.

How to identify lichens on trees

Lichens on trees are relatively obvious.  They typically have tones of green, gray or white hues and they come in all types of shapes and sizes.  Though they tend to look like flat circular shapes, they can come in all sizes and forms.  They can be spotted throughout the tree or they run vertically up and down the tree.  They can be sporadic or frequent.  Sometimes they have a thick, scaly, protruding rough texture and other times they are flat and flush against the bark of the tree.  Although there are over 13,000 different types of Lichens, they can be very adaptable to extreme climate zones.  Most, however, will prefer relatively mild, humid climates that get above average sunlight.  Because there are so many variations, they can look distinct from the typical description.  Most will look like a mossy, furry growth on your tree.

Do lichens grow in polluted areas?

Lichens are very widely used as environmental indicators.  If the air quality is very poorly polluted with elements such as sulfur dioxide or lead, fungi will likely not be found – only algae.  If the air quality is clean then you will see an abundance of shrubby, scaly, hairy Lichens.  The most sensitive lichens (don’t tolerate pollution) are shrubby and hair while those that are more tolerant are crusty in appearance.  Crusty lichens tend to reside in urban areas and populated cities where pollution tends to be higher than in rural towns.  You can also find these types of lichens in industrial zones that release more pollutants than normal.

Although lichens can appear to be harmful to a tree, they are actually completely harmless and provide a habitat for certain fungi and algae to co-exist and mutually benefit from each other.  If you are not sure whether your tree has lichens or potentially other harmful bacteria or fungi then you should contact your local tree care experts who can put together a plan for pest control and disease management for your tree.