I had a locust tree cut down a year ago because one or more roots were begin I g to lift some patio bricks and I am sure it is probably under the concrete slab. I also have sprouts coming up that I have been killing with chemical. I also had the stump ground down. Even though it is cut down, do the underground tree roots continue to grow? HELP!

Yes, black locust are clonal trees that have the ability to send up shoots from anywhere on their root system. When they are damaged, it tends to stimulate them to sucker and often leads to a jungle of small sucker sprouts coming up around where the stump was. I know it is too late for this time around, but, with clonal trees, it is best to immediately treat the stump with a strong chemical after cutting the tree down or, better yet, girdle the tree and apply chemicals in the girdle ring before cutting it down. That will help reduce the suckering. At this point, you will need to continue treating the suckers and eventually you will exhaust the root system's energy stores.