First of all, find where those saplings are coming from. If you don't, you'll be doing battle every year. After using Roundup for years, I was having to spray every year. Found this stuff at Home Depot a couple years ago. Haven't had any problems since.
https://www.homedepot.com/p/BIOADVAN...4655/203029601
But diesel works well, too. Just make sure you don't throw your blunt on the area for a few days.
