I feel your pain, mostly because I live your pain. TOH are the worst noxious weed I've ever dealt with. (My husband would argue oak tree seedlings are running a close second though) Unless the tree removal guys poisoned the stumps, you are dealing with very extensive, very enthusiastic root systems from 15 or 20 trees. The seedlings are easily dealt with by pulling or spraying them with roundup but the suckers... Your best bet is spot spray them with brush killer. I keep an old 409 spray bottle of full strength brush killer on hand for just this purpose. The only way to kill them is by stressing the roots. "Just keep pulling them" would be good advice with any other tree but for TOH, that's encouragement. Good Luck!
