Answer: Your lilac shrub spends all summer developing flower buds for the following spring's flower display. Don't prune your shrub now or you may accidentally prune off the flower buds! Wait until after the flowers are spent and then prune your shrub. You can completely remove the lower, spindly branches, or you can simply cut the entire shrub back by one-third to promote a dense, bushy growth habit. Do this as soon as the flowers are spent so your shrub will have all summer to produce flower buds for the following spring's floral display.
Best wishes with your landscape!
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