Answer: Your photinias, at 15 feet, have probably reached their maximum mature height. At this point major rehabilitation will take a couple of years. If you cut them back too severely all at once, they may not recover. Simply attacking it with clippers or a chainsaw to reshape it isn't a good idea either. Start by reaching as deeply inside each shrub as possible, and removing branches at the trunk. Try not to remove more than about a third of the shrub this year. Next growth season, reduce the height of theshrubs with some more selective pruning. By the third growing season, you should have a more manageable sized shrub and can begin to cut back the growing tips of the shrub to make it bush out. Take your time, and you'll eventually have the sized shrubs you want. You may have to compromise on the height, though. Four feet isn't very tall for a Photinia.
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