Certified GKH Gardening Expert
If you're pruning to a tree-shape, remove the lower branches to reveal the trunks, removing the lower branches to shape it into a tree. Prune all the young suckers around the base of the shrub at ground level, removing up to one third of the shrub's stems if there are multiple trunks rising from the roots. Do not remove any more than a third of its growth in any given year. Also, remove any crossing or crowded branches about 1/4-inch above an outward facing bud until you achieve the desired shape.