treepro logo

 Santa Rosa: (707) 528-3300 - Sebastopol: (707) 829-3300 - Healdsburg: (707) 433-9400


  • Home
    Home This is where you can find all the blog posts throughout the site.
  • Categories
    Categories Displays a list of categories from this blog.
  • Tags
    Tags Displays a list of tags that have been used in the blog.
  • Bloggers
    Bloggers Search for your favorite blogger from this site.
  • Team Blogs
    Team Blogs Find your favorite team blogs here.
  • Login
    Login Login form

Oak root fungus is the culprit in many oak tree failures

Posted by on in Uncategorized
  • Font size: Larger Smaller
  • Hits: 5381
  • Subscribe to this entry
  • Print

b2ap3_thumbnail_oak_failure2.jpgb2ap3_thumbnail_mushroom.jpgb2ap3_thumbnail_mushroom2.JPGb2ap3_thumbnail_oak_failure.jpgToday I inspected a fallen oak tree in Windsor which broke off at the base and ended up in the neighbor's yard. As the tree fell, it broke several large limbs off an adjacent oak in the other neighbor's yard. The tree fortunately did not hit the neighbor's home but did knock part of the fence down and damaged shrubs and trees as it fell.

I inspected the root crown of the tree and found decay present--most likely caused by root fungus. The tree looked healthy, but under the ground the roots had slowly been rotting away. The tree was approximately 70 to 80 years old and the home and subdivision were built around the existing native oaks. When construction projects meet established heritage oak trees the results can be detrimental to the health and structure of the trees. Heavy equipment can cause extensive damage if operated over the roots of trees. Root fungus also develops If the soil level is changed around trees. Installation of utilities and trenching within the root zone of the tree can damage roots and lead to decay of major support roots. Equipment can also damage the branches or trunks of trees which leads to decay at these wound sites.

Currently there are stricter standards for protecting native trees during development. Cities such as Windsor, Santa Rosa, Sebastopol, Healdsburg and others have strict guidelines designed to prevent damage to heritage trees. In older developments built in the 70's and 80's many cities had yet to develop adequate protection measures for trees.

How to identify potential root fungus problems

In the case of this tree failure there were no obvious signs of decay at the root zone that led to the tree toppling over. The soil level at the root zone may have been changed. Trees that have buried root zones will have a trunk that does not widen at the soil level. Normally, older native oak trees show a widening where the main roots extend from the lower trunk area. This root "flare" indicates that the soil level has not be raised around the tree.

Another indication of potential root fungus or decay is the presence of mushrooms at the base of the tree during the winter. Honey-colored clusters of mushrooms are a strong indicator of armallaria mellea fungus that can cause damage and loss of structural integrity to the roots. There are also other "fruiting bodies" that may be found at the base of oak trees. Growths such Ganoderma appalnatum may indicate decay at the trunk of the tree.

Cavities or holes in the trunk may also indicate a structural defect in the tree that can extend into the main roots of the tree. Performing a root crown excavation where the soil is carefully removed around the trunk of the tree gives a more accurate appraisal of potential decay at the root zone. Certified Arborists are a good resource for completing root crown excavations.

Contact one of our Certified Arborists to inspect your trees for structure and overall health. In my next blog I'll discuss who is responsible when a tree falls from one property onto another and causes damage. The answer will surprise you unless you've had first hand experience of this situation.



  • No comments made yet. Be the first to submit a comment

Leave your comment

Guest Monday, 27 June 2022