Learn which plants thrive in your Hardiness Zone with our new interactive map!

Tree Fungus Growth

By Bonnie Grant ; Updated September 21, 2017
A fungus growing on a tree can indicate that the tree was already in some stress.

Trees of all kinds are susceptible to disease and pest problems. The growth of fungi is one problem that can form on the trunk or roots of a tree and can be an annoyance or lethal for the plant. The presence of fungi on a tree is not a good thing since it is indicative of stress or disease in the tree. Fungi come in many varieties, shapes and hues and can be easy to control or a common plague like Texas root rot.

What is a Fungus

A fungus is an organism that feeds on decaying and rotting matter. It is an important part of the ecosystem and is the original recycler. A fungus is often initially classified by its fruiting body, which is the part you can see. There may be a stem, gills, net, and other topical features to help identify the fungus. Color, texture and patterning are important do distinguish the different types. The bulk of a fungus is under ground or out of view. The fruiting bodies sprout from mycelium which are the network of individual threads called hyphae. These secrete enzymes that break down organic matter into particles small enough to be absorbed.

Fungi Growth

Fungi feed themselves on the organic matter they break down and absorb. This is their method of gaining nutrition since they have no ability to photosynthesize and create their own food. When a fungus has exhausted the food in one area it branches out and the mycelium in the center die. This is why mushrooms often grow in a fairy ring with all the fruiting bodies outside a center in a circle. Fungi can grow in any organic matter and tree fungi are not exception. Some tree fungi prefer dead wood and others prefer live. Some prefer conifers and other deciduous trees. Location is organism-specific for most fungi.

Tree Fungus Propagation

Tree fungus spreads just like any spore-producing mushroom. The fruiting body or exterior will ripen and release spores. The spores are carried on wind or by animal movement to a hospitable environment where they begin to produce a web of mycelium and begin the fruiting process again. Tree fungus spores land on wounds in tree bark. They begin to feed on the damaged tissue as they send out mycelium to grow. Some send threads of mycelium into the heartwood of a tree to eat that dead wood. Rotted wood drops to the ground and nourishes tree roots.

Types of Tree Fungus

Wood decay fungi usually eat dead and decaying tissue but can eat live tissue. They can be present in very obvious forms such as conks or shelves or not be evident to the naked eye. Rust fungi are very contagious and move from tree to tree. They remain alive with the tree until it is dead. Canker fungus is introduced through damage or wounds in the tree and will kill its host. It spreads easily and kills the bark first. Root rots such as Texas or Cotton root rot are harbored in soils and can have epidemic spread rates. The fungus attacks and lives on roots of trees, impeding their ability to uptake nutrition that the tree needs to survive. Root rots can kill the tree. There are numerous new fungi coming into the area as we import different plant species.


When trees are pruned and especially when limbs are removed, the cut needs to be made to leave a branch collar or protective area around the cut. The branch collar is callused wood that grows around a wound. It will protect the plant from alien tissue entry. Never cut into the trunk and make cuts clean. Overly wet plants are good breeding grounds for fungal spores, especially in warm humid areas. Application of anti-fungals before the wet season may prevent some fungus of trees.


About the Author


Bonnie Grant began writing professionally in 1990. She has been published on various websites, specializing in garden-related instructional articles. Grant recently earned a Bachelor of Arts in business management with a hospitality focus from South Seattle Community College.