Knowledgebase
Lilacs - how to renew #751414
Asked May 22, 2021, 12:43 AM EDT
Hennepin County Minnesota
Expert Response
The dead branches can be pruned out and they won't count when considering how much you're pruning over a 3 to 4 year period. For renewal pruning, take out about a third to a quarter of the live material by removing the biggest stems to the ground.
In your case, I recommend pruning out the dead stems then standing back to see what can be done with the live portions. It may even be advisable to leave it alone after a year to see if new stems sprout where the dead stems have been removed. They may start this summer with the increase in sunlight to that portion of the shrub.
You may already have this link but it contains excellent pruning information including details about renewal pruning from the U of MN Extension.
Good-luck!
Hello –
After removing most of the dead wood in May, these pictures show how they look in mid-July. I live in an HOA and we have questions on how to best proceed next.
-Is renewal feasible? Some new growth is starting at the bottom. Some mid-plant branches that were questionable now have immature leaves forming. Especially with this hot, dry weather are they viable?
-Some residents would like to trim this year’s new growth at the top at this time. We assume this will result in no blooms next year. Aside from that, would this harm the lilacs, and when should it be done?
-If renewal is not likely to be successful, and we rejuvenate by cutting the bushes down near the ground, what should the height be and what time of year is best to do this? How long should we expect it take to grow back to a medium height?
Thank you. We very much appreciate your recommendations.
From: Ask Extension
Sent: Sunday, May 23, 2021 3:05 PM
To: karenchese2
Subject: Re: Lilacs - how to renew (#0021345)
I think rejuvenation pruning next spring (late winter) would be best. Either type of pruning will result in few to no flowers. Leave them as they are now so that they'll be able to store the energy needed to start afresh after cutting them down. You could cut them to the level of the low growth I see in your recent photos, maybe nine to 12 inches. They'll spend most of next spring and summer growing new canes, adding to existing canes, and setting flower buds for the following year. They won't look pretty now but the leaves that they have will help set them up for success next year.
Good-luck!
