Tales From the Help Desk: Growths on Tree Bark

Q:  Something is growing on the bark of my tree.  Is that a problem?

A:  It depends.  If it is flat and looks rather lacy, it’s lichen and does not harm the tree. If the growth on your tree bark is shaped like a shelf and looks like a mushroom, it is a conk. Conks indicate that the tree has internal decay.

Lichen is a symbiotic relation between certain types of fungi and algae. They have a very shallow attachment to the tree. The fungi provide moisture to the algae. The algae provide food to the fungi. Lichen tends to be flat and look somewhat like a doily.

Neither fungi nor algae are plants. Fungi cannot make their own food but decompose and absorb organic material from other living things. Algae contain chlorophyll but they do not have stems, roots, leaves, or vascular tissue. Lichen may look a bit like moss but are not mosses. Mosses are primitive non-vascular plants.

While lichen do not harm trees, they may be found on trees in poor health. The A&M Auburn University Extension article “Lichen on Woody Trees and Shrubs” states, “Heavy infestations of lichens are most common on shrubs and trees in declining or poor health due to other factors.”

Removing Lichen and Conks

If you do not want lichen on your tree because you just do not like the look of it, it can be removed with a soapy solution and gentle brush. Care should be taken to not damage the bark.

Conks are shelf-like structures that appear singly or in rows and columns. Conks are caused by certain types of fungi and present in different color patterns and shapes. They may also appear as mushrooms growing from the tree root flare or surface roots. Conks are the fruiting body of the fungi. Internally, these fungi feed on the wood of the tree and produce enzymes that cause the tree to rot. Once you see conks on a tree, there is already serious damage to the tree. Removing the conks does not remove the damaging fungi inside the tree.

Some conks are edible and can be dried and used for tea, and some can even be used for medicinal purposes. But others are not edible and can be toxic if ingested. As one would do with wild mushrooms, if in doubt, throw it out.

This article first appeared in the July 2022 edition of the Colonial Master Gardener newsletter.