I have pruned trees that were growing suckers, and now the stump of the suckers are growing more suckers! How do I stop this from happening? And what should be done about trees that continue to sprout from a stump that's been there for a decade?
Cut the suckers and paint the fresh cuts with concentrated Round-Up. The tree will suck the Round-Up into its system and kill it. It may take a few applications, but will eventually kill the roots.