two 9-year-old philodendrons removed and need to kill the roots

Question

I also had two 9-year-old philodendrons removed and need to kill the roots. I need to know what to put on the roots of the philodendrons to kill them for good due to my 5-year-old dog Gigi (Cockapoo)!
Please tell me what to use on the roots so they won’t come back too!

• 

Answer 1

I take it you've already cut the plants down? Treat the trunks as advised in this article for killing trees with herbicide and by cutting them down: https://www.gardeningknowhow.com/ornamental/trees/tgen/how-to-kill-a-tree-killing-trees-in-your-garden.htm