Answer: You'll want to wait until after your lilac blooms and then you can remove up to about one-third of the growth on your shrub. To encourage new growth at the bottom of the plant (they tend to get woody at the bottom), completely remove a few of the upright stems. Then prune the rest of the top back. Don't remove more than about a third of the shrub in any one pruning session or it may become too stressed to develop flower buds for next spring's floral display.
Enjoy your lilac!
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