Garlon won’t kill sweetgum. Mixing Roundup in with imazapyr will help, to be fair. Certainly you can ding hardwoods if it gets in the root zone, but folks make a lot more out of it than what is reality. If oaks died every time some got in the root zone utilities would never use it on their ROW. You can spray a lot of products that will knock it back, but without imazapyr in the tank I’d bet you won’t kill much more than half of it. It is the go-to product for sweetgum.

If you do have serious concern and you have trees you want to keep that are fairly close, there isn’t anything wrong with being overly cautious. Safe is not sorry, I like to say. You can whittle away at it with a multi-year approach.

If you do the things you need to do when you need to do them then someday you can do the things you want to do when you want to do them.