Q: We recently bought some rural property that has quite a few lovely old oak trees. At the base of the trees are thick hedge bushes. How can we get rid of them without hurting the oaks?
A: Since you are so attached to the trees, I think this is a situation where it is better to be safe than sorry. I don’t think you should use a herbicide. I know of a situation where a public institution decided to remove a couple of large crape myrtle trees that lined a sidewalk. Rather than pull them out, they sawed the plants off at ground level and painted Roundup on the stump to prevent resprouting. Unfortunately, they didn’t realize that adjoining crapemyrtle roots had grafted to each other underground. Consequently, the Roundup was transported from the stumps to nearby trees, which died.
On the slim chance that the bushes under the oaks have grafted to the oak roots, don’t spray them with weed killer. Instead, cut the bushes at ground level and continue removing sprouts for a year. By that time, the shade and the lack of leaves on the bushes will kill them without harming your big trees.