I have a client who wants me to put landscape border stone and mulch, in a ring around some small trees. The stone she wants, would have to be dug in about 4 inches as she wants them at grass level for the mower so no trimming will be required. Approximately 8' tall, all of them. One is a maple, one is a Blue Spruce, one is a White Birch and one is an Ash. I probed around the base of the trees and all seemed ok to go except the Ash. There are roots very close to the surface. I mean a lot of them, radiating in all directions from the trunk. I would have to cut these roots at about 3 feet from the trunk to install the border. I mentioned my concern and she said "Don't worry about it. If the tree dies, it dies." My question is, what is the probable harm from cutting these roots? My second question, even if the tree might die and the customer says do it anyway, should I do it anyway?