Trimming lilac bushes #772763 - Ask Extension

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Trimming lilac bushes #772763

Asked September 22, 2021, 9:33 PM EDT

My 55 year old lilac bushes have never been trimmed. They hardly bloom the last few years. I know if I trim them now, they will not bloom in the spring. They are so big, now three feet below my power lines. Instead of trimming out the old wood, can I cut them down to four or five feet tall? Will they regrow? Thank you for you help, Cindi

Dakota County Minnesota

Expert Response

You are probably going to have to sacrifice blooms for next spring.  However, you can trim them back to the four/five feet but I also recommend that you cut out 1/3rd of the oldest, thickest stems right to the ground.  Those old stems do not bloom well and removing them will encourage new growth from the ground level.  After the blooms fade the following year, trim the stems back some and again cut out another 1/3rd of oldest stems.  Repeat the following spring and your lilacs will be like new young shrubs.

Barbara Harlan Replied September 22, 2021, 11:06 PM EDT

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