I just mowed down a large area of vinca major and surprise! There is a thick basketweave of wisteria vines all over the ground. Have been trying to dig them out, but its really hard. If I use roundup will the death juice go all the way back into the mother tree wisteria, which I don't want to kill? I will try to sever the long runners from the mom, but I may not get them all separated. Sneaky plant.