Hello. I asked this question quite a while ago and the answers I recieved were very helpfull but I'm afraid did not solve my problem so I'm hoping someone can come up with some new ideas....I have a rosebush growing on my backyard wall which is very pretty but unfortunately the roots are burrowing beneath the top course of bricks and forcing said bricks apart and making them unstable....As I said I recieved many tips on what to do...various cococtions of sprays etc but nothing seems to have worked. I am thinking of trying to burn it out with a blowtorch but that seems a bit extreme so any new ideas would be greatly appreciated. Sorry for the longwinded message.
Cut off all visible growth and cover the area with a piece of black plastic this will kill the plant as it will not be able to produce food then clear out the rest of the dead roots
I defeated the dreaded ivy that was under my garden wall by sawing through a thick bit low down, and covering the cut with one of those really strong weedkillers like root-out. Then I tied a plastic bag over the area I'd treated so it couldn't wash away in the rain. It killed off the ivy but it took about three months in all. Same treatment worked on the lilac tree.