I have hedges with very aggressive roots that are continuously growing into the connector of my sewer system, causing back ups and costing money to get the line snaked.. They are wildly overgrown and need to come out. What is the best way to kill them. I have cut them down and cut off all the branches (in the hopes of them coming back next year) but have decided that due to the root problem, they should just come out. What chemicals could I use to kill them. I don't have a truck or chain, or I would just pull them out. Any help given is much appreciated!