Ask a Consulting Arborist Q&A: Root and Soil Concerns

Q: Will a large pile of dirt on 1/8 of a root system suffocate and kill the tree?

Thursday, December 31, 2015  

Q: I recently had a berm built on my property. The contractor piled some of the dirt (dense clay) near a large live oak tree. The fill encroaches 4 to 5 feet into the tree's large canopy (but still is 20 feet from the trunk). If you imagine a circle, the area where the fill encroaches under the canopy would be about 1/8 of the circle. My question is whether or not the remaining 7/8 of unencumbered root system would be sufficient for the tree to continue to live, or is 1/8 coverage from the fill going to hurt/kill the tree?

A: Usually the maximum area of roots that is allowed to be damaged at one time from root cutting, compaction, or otherwise before expecting dieback in a tree is 10-20%. The desciption of impacts you state should be acceptable, given the rest of the root area is not being impacted. You can look up CRZ (Critical Root Zone) areas and issues on the internet if you want to follow up more about root impacts and how to reduce damages to trees.


Responder: John Harris, RCA #468, Hollywood, FL