Many homeowners and property managers are surprised when the arborist or tree-care professional they enlisted to prune a tree, spends the bulk of his time explaining the dangers of a tiny little mushroom, growing out of their 100-foot-tall tree.
Surely such a tiny, insignificant little outgrowth poses no threat to the mighty oak growing above it – or does it?
People tend to view mushrooms as rather benign components of the natural world, whether they are growing in the forest or on the trees beside their homes. But in actuality, mushrooms provide important clues about often-unseen world. And while they don’t always foreshadow future tree problems, their presence should never be ignored.
The Anatomy of a Fungus
Mushrooms are the fruiting bodies of fungi. Functionally similar to seed pods, most mushrooms contain millions of tiny spores inside their gills. When the time is right, the mushroom releases its spores, and they float in the wind, until reaching a suitable growing site. There they will start a new fungal colony and begin the process anew.
But while mushrooms are visually obvious, most of a fungal colony lives out of sight. The exact location in which they grow depends upon the species in question and its preferred food source, but many live in the soil or the wood of trees. Taking the form of numerous threadlike filaments called hyphae, the fungus lives in these places, digesting various tissues with which they are in contact. The hyphae will produce mushrooms that break through the surface of the soil or tree once the environmental conditions are right.
You can see these hyphae for yourself by venturing out to the local forest and scooping back a bit of soil. Often, you will see many white or gray threads heading in many directions – these are fungal hyphae.
Decay, Destruction and the Circle of Life
The feeding activity of some fungal hyphae can break down the cellular structure of a tree’s wood. As this happens, the tree’s structural integrity is compromised, and if allow to progress for a length of time, large branches may drop or the entire trunk may fail.
And this is why your arborist spent more time worrying about the mushroom than he did pruning your tree. Not only does the presence of this mushroom indicate that the tree may require removal, it serves as a warning that the branches and trunk may have already become instable. He may not even be able to climb the tree safely.
But it is important to remember that while fungi may be deadly for your growing trees, these same organisms are necessary for life on earth. Were it not for these wood-eating fungi, the world would be overrun with dead trees, and the nutrients inside the dead wood would be forever removed from the food chain.
Additionally, fungal decay provides opportunities for many animals. For example, red-cockaded woodpeckers of the southeastern United States are unable to penetrate the healthy hardwood of the longleaf pines growing in their native lands. However, the birds easily excavate nests in pines that have advanced heartwood rot (which results from fungal decay), as the rot softens the wood considerably.
Not All Mushrooms Are Alike
It is important to recognize that the world is home to thousandsmillionsof different mushroom-producing fungi, and not all of them are destructive to trees. Some, for example, feed on organic material in the soil more than the roots or the tree’s tissues. Accordingly, mushrooms do not always indicate a problem.
The best strategy for dealing with a mushroom growing from your tree’s trunk or roots is to contact a qualified arborist, who can identify the mushroom (often by sending it to a diagnostic laboratory for analysis) and then recommend a prudent plan of attack. The tree may require removal to ensure continued safety, but the arborist may also be able to simply remove an infested branch; if you are really lucky, he’ll tell you that the mushroom is from a non-pathogenic fungal colony, and you don’t have to worry about it at all.
But in all cases, prompt assessment is crucial so contact your favorite arborist without delay.