I have a number of apple trees with grass growing under them right up to
the trunk. I want to get rid of the grass and mulch under the trees out
to the drip line.

What is a good way to do this? I'm tempted to use an herbicide (like
Roundup) but I'm not sure what that would do to the tree. I have enough
trees that I don't relish the idea of digging around under each one of
them and possibly messing up the roots. I think if I put mulch down on
top of the grass, the grass would just grow right through the mulch.

Any suggestions?