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lilac bush pruning #899823

Asked May 02, 2025, 9:36 PM EDT

I live in "Boulder". I have some large (12') lilac bushes in my yard. When ,how and how severely can I cut them back (prune) them? They are also six to eight feet in diameter. How shouls I trim back the diameter? .. Thanks for whatever help you can geve me.

Boulder County Colorado

Expert Response

Paul,

Lilacs are one of those shrubs that needs pruned to encourage it to
flower year after year. You will need to decide if you want to prune the
lilacs for shaping, thinning, or a rejuvenation. Since it is a spring
flowering shrub, the best time to prune it is after it is finished
blooming.

The following 2 articles provide useful information about pruning lilac shrubs.

https://planttalk.colostate.edu/topics/trees-shrubs-vines/1729-renewing-shrubs/

https://cmg.extension.colostate.edu/Gardennotes/616.pdf

We hope this provides the information you need.
Colorado Master Gardener Help Desk
An Ask Extension Expert Replied May 07, 2025, 9:25 PM EDT

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