Answer: These plants should not be cut back until the new growth is apparent and growing vigorously. At that point, trim away any winter damaged wood and then shape lightly. Do not remove more than a third to half of the plant and do not cut into older harder wood. trimming them back too early may have shocked them or exposed then still-living wood to excess cold. At this point, wait until early June before giving up, sometimes they leaf out very late. You may trim them again for shaping right after they bloom, usually all that is needed at that point is a light trim to remove the faded flowers and encourage addtional bushiness.
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