Question
My tree is about 15 yrs old, bought at a nursery,grafted and planted by experts. The roots spread all over my from yard about 4-6" deep, and are sprouting everywhere. I try to pick them before mowing. Is there any way to stop it from happening?

Answer
Cutting the sprouts is usually the best method. If you were to use a herbicide the parent tree may be damaged. You might try a growth retardant. Have not heard it used on sprouts but it is used to slow or stop growth of bushes and trees. They are sprayed on the sprout foliage and the growth is slowed way down but they will not damage the tree. I would try it it can not harm the trees and there is no reason it will not work. Check with your local tree nursery for these growth retardant products.
here is a web link to one of these products. http://www.montereylawngarden.com/faqs/suckerstopper/
I would just keep mowing them when you mow they will stop on their own. OR try the sucker stopper.