How to Grow: Lilac Pruning

Learn how to prune and care for lilacs in this video. It includes information on pruning an overgrown lilac.


Everyone loves lilacs these beautiful spring flowering shrubs have fragrant flowers that add lots of color and they’re great harbingers of summer. They can be grown as individual plants around the house or in the lawn or even as a hedge plant. They require little care and faithfully produce flowers every year as long as they’re happy. But lilacs do need six to eight hours of full sun a day. That way they’ll actually bloom their best. Some of them can grow really big so you have to prune them every year to keep them a manageable size. If you don’t they’ll grow into monsters so this is. How do you prune lilacs?

These are the dead seed heads that are there after flowering. With a hand pruners snip off the dead flowers before they form seeds. This not only tidies up the plant it allows the shrub to send more energy into growing leaves and flower buds and less into growing seeds. Some people think that if you don’t deadhead you won’t get as many flowers next year. I’ve noticed, though, that if you have an older, stronger shrub that’s not the case. But with weaker, younger shrubs leaving the dead flowers in place may inhibit flower buds from forming the next spring.

After you’re done with deadheading you’ll need to prune your shrub to keep it a manageable size. You have to do this within six weeks after flowering because after that they’re forming their flower buds for next year. If you go and prune like in July, August, or September you may be pruning off flower buds for next year. You get fewer flowers. Here’s how to prune.

You want to take your branch back to side branches here and prune right above that. Cutback individual branches to just above a set of leaves or a side branch. This will stimulate the side branches to form and reduce the height. Cut to a height below what is ultimately what you want so it has room to grow back again. Avoid using hedge trimmers to cut everything even. The lilac just ends up looking like a gumdrop and doesn’t flower very well.

For overgrown lilacs like this one, you can prune it right back to the ground or even to a stump that’s a couple feet tall and it’ll grow back and eventually flower again. A better way to prune it is using a three-year rotational pruning technique. This way you prune out a third of the bush every year and you’ll never stop having flowers. Let me show you how to do that.

Remove one-third of the largest branches the first year to the ground or even to a couple feet tall. This will stimulate suckers to start growing. Select the best two or three suckers and remove the rest. Prune out the second third the next year and then do the same pruning of the suckers. After about three years the first year suckers will be large enough to flower and the shrub’s height will be reduced to a manageable size.

So deadheading your lilacs and pruning them to the right height every year will make a beautiful lilac that will flower for you every year and be a manageable size.

Go here for more on growing lilacs.