Answer: Although you ground the stump, the roots are obviously still underground and still very much alive. They will persist in sending up shoots until all of the stored energy is depleted. Depending upon the locations of the sprouts you might be able to hasten the process by pruning them at ground level and then painting a small amount of Round Up or other vegetation killer on the stubs. Round Up will kill other plants so if these suckers are popping up in a lawn, don't use the herbicide. If they're popping up in bare earth, go ahead and paint the stubs immediately after pruning. The bottom line is - the suckers are being sent up by the roots in an effort to reach sunlight and to have the sprouts and their leaves convert sunlight into carbohydrates to nourish the roots. As long as you keep the sprouts cut down as soon as they appear, the roots will expend more energy sending them up than they get in return through photosynthesis. The result will be that the roots will eventually use up their stored energy supply and will die.
Best wishes with your landscape!
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