I can't say for sure, but I had a filbert (hazelnut) tree growing smack up through the middle of one of my favorite big rhododendrons. I cut it down twice, and it just kept coming back. I finally talked to the people at a good local nursery, and they told me I had to cut it down again, spray the stump with brush killer, wrap it in black plastic and cover the whole business with an upturned bucket or half-barrel. (They said if it got any light, it would resprout.) I did that a few weeks ago, and the rhody is just starting to bloom. The leaves aren't showing any evidence of being damaged by the brush killer. I was very careful, of course, not to get any of the brush killer on the rhody's trunk, branches, or leaves. In fact, I painted it on the stump of the filbert, so there wouldn't be any chance of spray drift.