Clear the trunk of the tree from all of the additional dirt added. When you pile dirt or mulch above the rootball you are doing what’s called “volcano mulching”. Search on the internet for volcano mulching and Mike McGroarty. Mike is a nursery man in Ohio and has a recent post about this. Yes, you will suffocate the tree, and possibly cause the tree to form advantageous roots in the new higher layer of soil that usually end up growing around the tree trunk and girdling (strangling) them. Also, driving heavy equipment within the drip line will compact the soil and crush some roots that also hurt the tree.
When I bought my place, the drive into the property went past a house with beautiful mature willow trees at the entrance. Dumbass owner, also a developer, thought it would look “better” if he piled dirt over the roots and put large stones on it. Not only did he destroy a beautiful vista, but now three years later the willows are falling over dead. I’ve taken landscaping and horticulture certificate courses for my business and volcano mulching is just wrong. When you drive around look at some of the nicely landscaped and maintained commercial properties and the “professional” landscaping companies do this on a regular basis. That’s it for my rant.
