Fruiting Location

The general location a wood decay fungus fruits on a tree is an aid to identification. Four locations are identified here including on the ground attached to a root away from the base of the tree, on the butt or buttress roots of the tree, on the main trunk above the roots, and on the upper trunk and larger diameter branches. Fruiting on the ground next to a tree requires that the fungus actually be attached to a woody root for it to be a root decay pathogen. Several fungi that do not cause decay but are commonly found on the soil next to a tree are included in this site because of their similar appearance to common wood decay fungi.

Ground- Woody Root

Many of the root and butt decay fungi fruit on the ground away from the base of the tree (Photograph 1). Some may fruit a substantial distance (5-20 feet) away from the base of the tree (Photograph 2). This can make them hard to separate from fungi that are saprophytes on decaying organic matter that also are common around urban trees and in urban lawns. There is no easy way that a fungus fruiting away from the base of a tree can be verified to be a decay fungus without positive identification or by digging and verification of its attachment to a woody root.

Photograph 1. A potential root and butt decay fungus fruiting on the ground near the base of a white oak.
Photograph 1. A potential root and butt decay fungus fruiting on the ground near the base of a white oak.
Photograph 2. A root decay fungus Armillaria tabescens fruiting in the lawn a good distance away from the base of an infected silver maple.
Photograph 2. A root decay fungus Armillaria tabescens fruiting in the lawn a good distance away from the base of an infected silver maple.

Buttress roots, and/or Base or Butt

A substantial number of wood decay fungi fruit at the base of the tree attached to large diameter buttress roots, or the butt or lower portion of the main trunk of the tree (Photograph 3). Most of these fungi also decay the lower section of the main trunk and may also decay roots. Several of the common decay fungi of urban trees seldom if ever will be found fruiting higher than three feet off the ground in the tree.

Photograph 3. Ganoderma lucidum fruiting on the butt and woody roots of a Norway maple.
Photograph 3. Ganoderma lucidum fruiting on the butt and woody roots of a Norway maple.

Main trunk

Fruiting on the main trunk is common for many decay fungi. Some of these fungi may also fruit lower or higher in the tree on rarer occasion but the main location they develop is on the main trunk of the tree above the buttress roots.

Photograph 4. Fruiting on the main trunk of the tree is a common location that many decay fungi are found.
Photograph 4. Fruiting on the main trunk of the tree is a common location that many decay fungi are found.

Upper Trunk or Branches

Some decay fungi usually develop their fruiting on the upper trunk above where the scaffold branches attach and larger diameter branches (four inches and greater). Many of these fungi can be found lower in the tree also but are more common higher in the crown.

Photograph 5. Polyporus squamosus fruiting in the mid-crown of a horsechestnut. Many decay fungi are found primarily higher in the crown and on larger diameter branches, although fruiting lower on the tree is also possible.
Photograph 5. Polyporus squamosus fruiting in the mid-crown of a horsechestnut. Many decay fungi are found primarily higher in the crown and on larger diameter branches, although fruiting lower on the tree is also possible.