Q: We have smilax growing up into a dogwood tree through large azaleas. What will kill it?
A: Smilax is very tough to kill with any method other than pulling it or digging it out. If you excavate the roots, you’ll see there are many swollen yellow nodes along the root. Each node can sprout into a new thorny smilax vine. No herbicide is able to move down the vine and into the length of the roots to kill all the nodes: some inevitably survive and become problematic again. It’s easiest to dig a smilax when you have a helper. One person can pull and the other can operate a shovel or mattock to get everything out of the ground.