Certified GKH Gardening Expert
Trees tend to sucker when they are under stress. Lack of water is the most common reason for this, but there can be others. Some trees, like grafted trees, are always under a little stress and will always put out some suckers. You can reduce the number of suckers a tree puts out be removing stress from the tree. Make sure it is well watered and fed and that there are no pests affecting the tree.