About fifteen years ago I planted a couple of rose bushes that must have been grafted onto different root stock. Every spring I got branches from the base of my lavender roses that bloomed red, and every spring I cut away these branches. Last summer I was so unhappy with the growth of these root shoots that I dug up my rose bushes and had to use pruning shears to cut the roots. I thought I had destroyed those red shoots forever, but guess what...now they are popping up in the garden! How can I get rid of them without using an herbicide?