What is the Stuff Growing on the Side of My Tree? - Ask BrightView


Ask BrightView: Episode 11

Lichens, a symbiotic relationship between an algae and a fungus, are often mistaken as something harmful and sometimes thought of as a disease on trees. BrightView Horticulturist Corine Ferre explains why it is just the opposite and how it can take on many forms and colors.

(For the full transcript, see below.)

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Video Transcription

What is the Stuff Growing on the Side of My Tree?


As a horticulturist and an educator, I have been asked many times, "What is that stuff growing on my tree?"

That stuff is called lichens. Lichens are an epiphyte - it's a symbiotic relationship between an algae and a fungus. It is not harmful, much on the contrary. They just use the tree or the palm trunk as a support and it's a good sign. It means that there is no pollution around.


Lichens can have many different appearances, from a little bluish-greenish spot to little pieces that are protruding. Some of them can get tall and thick, while some of them remain very close to the trunk. Some are round and some are more oblong.

Growing Space

You saw lichens on a royal palm trunk and this here are lichens on an oak tree trunk. They can also grow on rocks or even cars that have been stationary for a long time.


They can have various different colors from the ones you saw on the royal palms, which were a silverish color. Here, you have some that are greenish, and they can also come in orange, yellow, or brown.

Space Travel

Believe it or not, scientists have encapsulated lichens and sent it into space, brought it back to earth, and examined it. The lichens did not change whatsoever. They were alive and not affected by its being exposed in space.