I recently built a large patio in my backyard around an existing mature 80' tall elm tree. No choice but to put the concrete around the tree. I did leave a 2.5 foot circle around the tree and had them build a raised bed around it about 20" tall. I filled the space with gravel up to about a foot from the top and then filled that with garden soil (mix of mulch and compost). The patio does not reach the drip line of the tree but is well back from that. The bed gets good drainage through the gravel. I can't tear out the concrete now but was wondering will this raised bed hurt it?
Raised Bed Under Elm Tree
Certified GKH Gardening Expert
Unfortunately this is a landscaping mistake.
Most active tree roots are in the top 3 feet of soil and the majority are in the top 12 inches of soil.
Roots will go out up to 3 times the canopy.
These roots need oxygen and water. They will find it, at the expense of your concrete.