Answer: You can renovate old, overgrown plants by cutting a few of the oldest stems to the ground each year. Heavy pruning will result in fewer blooms next year, but you'll have a more managable plant. Lilacs form flower buds for next year's bloom where leaves join the stems. Try not to prune the branches where you see two buds forming just above the leaves. As you're cutting back stems and branches, remove weak and spindly wood to encourage new growth from the trunk. Once you've gotten your lilac back in shape, you can keep it inbounds by pinching back new growth every spring after flowering.
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