Answer: Lilacs are large plants, so there is no way to keep it really small over time. If it is way too big for the spot where it is planted you might want to replace it with something else. Having said that, every year you can remove some of the oldest stems or trunks by cutting them off at ground level, cut them off very short. Also remove any new shoots coming up from the ground that are smaller in diameter than a pencil. This will renew the plant on an ongoing basis and can help keep it a little shorter. If you need to prune back branches to try to control size, the only "safe" time to do that is right after it blooms. I hope this helps.
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