I have just had a tree cut down but left a 15 ft. stump and small growths are appearing in my lawn. A person at my local Home Depot said I need tree root killer to stop these growths. Is this true or where can I purchase this root killer?

Your basically wasting your time. Make the lawn look pleasing by having the stump ground.

HD didn't have it? A real lawn and garden may. Extra strength herbicides will slowly do it.

If having it ground down gets to the top of your list, make sure it is ground down low enough to cut down the hump large trees raise up under them.