Our landscaper wants to raise soil level 20 " around existing, healthy Mexican Palm Trees. He said he will encase the trunks with 6 " of rock to keep new soil from suffocating trees. Will this harm our Mexican Palms?
Mexican Palm Trees
Certified GKH Gardening Expert
It is always risky to mound up soil or mulch around a tree, especially as high as 20 inches. This can lead to root rot and infections on the trunk, and can end up suffocating the roots. Gravel is better than soil, but it will still restrict air flow to the roots somewhat, especially since it will be so deep.
There may be a way to do this without killing the trees by adding perforated pipes around them, in the gravel, to provide aeration.
Another possibility might be to "transplant" the palms- dig them up and plant them in the same location after the soil level is raised- as described in this article:
Palms tend to recover better than other mature trees after transplantation because of their specialized roots.