​Trimming hedges properly is key to beautiful, full and healthy long-lived shrubs. The University of Florida recommends trimming shrubs while the new green growth is emerging.  The most common mistake people make when trimming a hedge is cutting the shrub into a sharply-edged box shape. It's important to trim a hedge so that the top is narrower than the bottom; this way, sunlight can reach all the plant's leaves. The bottom branches of "box-shaped" hedges usually thin out—and even die—from lack of sunlight. Hedges that have been improperly trimmed become top heavy with green growth, and leafless at their base which require rejuvenation pruning or replacement. Rejuvenate your shrubs by removing one-third of the plants old stems to the ground each year for three years.  For information on pruning to rejuvenate, call the Palm Beach County Cooperative Extension Service Master Gardener Volunteer Hotline at 233-1750 M-F 9-4.