Strange growths on large Post Oak - Ask Extension
I
have a large Post Oak in my yard that has developed some strange growths on the
trunk & several branches. They look like little knobs – mayb...
Knowledgebase
Strange growths on large Post Oak #155730
Asked October 04, 2013, 4:27 PM EDT
I
have a large Post Oak in my yard that has developed some strange growths on the
trunk & several branches. They look like little knobs – maybe galls or
burls? Are they harmful to the tree?
Is there a recommended control or way to help the tree?
I've had several arborists take a look at it, & no one can definitively tell me what this is -
Thanks!
I've had several arborists take a look at it, & no one can definitively tell me what this is -
Thanks!
Travis County Texas
Expert Response
I don't recognize these growths. I'll check with our plan pathologist.
These growths are a response to some kind of old wounds on the tree. They can be common on many different species of oaks. The exact cause of why the tree has responded with this "hyper" growth has not been determined. An insect might be involved, but I am more inclined to believe the crown gall bacterium, Agrobacterium tumefaciens, might be involved. There are cases of that bacterium becoming systemic in other hosts (pecan, grapes), and it is possible we are seeing the same in oaks. These knots on the post oak have been growing for awhile. As to what the original wound was, it is also difficult to say. Old hail damage? Poorly closing branch attachments? I can only speculate. Fortunately, these growths will not be detrimental to the health of the tree. If the tree is showing symptoms of suffering from some malady, it is not related to these knots.
