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A few years ago, when I went to grab the hose, I noticed a ton of branches had been torn off my lilac bush. I accused my poor husband of getting overzealous with the pruners. However, I soon discovered that the hack job was the work of a mother squirrel that was meticulously building her nest. She’d rip off a branch or two and then run to my chimney (that’s a whole other story). I was worried about the lilac coming back the following spring, but it has been flourishing. Lilac is among my favourite spring scents—when I work outside on my deck, I take deep breaths when they’re in bloom, as they sway in the breeze. When those fragrant blooms fade, it’s a good time for pruning lilacs. So I thought I’d share a few tips!
The perfect time to prune a lilac bush is after the flowers have bloomed and faded. Spring-blooming shrubs should be pruned right after they have bloomed. If you save the task for later in the season, you risk pruning off next year’s blooms (because next year’s flower buds form on the current year’s wood)—a mistake I made in the past with an unruly forsythia!
Tips for pruning lilacs
There are three maintenance tasks I need to cross off my lilac to-do list in the spring. I need to trim the dead blooms off, prune the shrubs, and cut out suckers that have popped up underneath. Most of the stems I’m dealing with are thin enough that I can use my hand pruners, but if stems are thicker, you may want to use a pair of bypass loppers. Make sure the blades are clean before you cut. And while the plant is blooming, use the same sharp pruners to snip bouquets. You don’t want to tear or snap off blooms, as this could harm the lilac bush.
Trimming off lilac flowers
Removing the dead flowers from your lilac bush will encourage more blooms the following year. The important thing when trimming off your flowers is that you simply cut off the spent flowers—don’t worry about any surrounding stems. If you can see next year’s blooms forming (two new shoots coming from the stem), simply focus on the spent bloom’s stem. You don’t want to cut off next year’s flowers!
Now with my dwarf Bloomerang, I want to encourage a second blooming, which should take place towards the end of the summer or early fall. Pruning off the spent spring blooms will encourage more new growth and more blooms for that second bloom time. I could also add a light dose of fertilizer that’s been formulated for woody plants, which will also encourage the shrub to bloom again.
Pruning lilac shrubs
A good rule of thumb when pruning lilacs is not to prune more than one third of a shrub’s stems per year. When one of my lilacs climbed a little too high towards the eavestrough, I simply trimmed those branches to a reasonable height. I then trimmed the spent blooms and called it a day. You can also do a bit of light thinning to encourage new growth.
A more aggressive pruning, perhaps on older shrubs that haven’t been regularly maintained, should be done in late winter or early spring. At this point, you want to cut out older wood and malformed stems, and keep the newer stems to encourage new growth. Cut the older stems down to the ground.
With the Bloomerang lilac, I’ll just trim any especially long pieces to maintain the shape of the shrub. Bloomerangs have a nice rounded habit in the first place, so you don’t have to worry about shaping the bush too much. Mine has been in the garden for a few years and it’s still nice and small and compact.
Removing lilac suckers
Another part of pruning lilacs is removing the suckers. What are suckers? Around my lilac there are a few new lilac trees—single stems a few feet away, shooting up from the soil, making their presence known. These are the suckers. I simply cut them off at the soil line (or slightly below). However stems close to the trunk of the bush itself, you may want to leave, as a healthy lilac has a mix of old and new stems. You could also dig up the suckers and replant them elsewhere. Who doesn’t love new plants?
This video offers a synopsis of these lilac-pruning tips.
More pruning tips
Learn how and when to prune these trees and shrubs:
Hello Tara – I find your posts very educational and informative. I have an enormous purple flowering lilac cultivar that has been growing since the 60’s. Many of the stems are over 1 inch in diameter, and some are nearing 2 inches – the main trunk is much thicker still. I am
Planning on using an electric pruning saw (functions like a miniature chain saw). I trust that this will be okay, as hand held pruners will not tbey able to cut through the old wood. I plan on doing this in late winter. Is this how you would approach this project. The large shrub is not very florific at this point – probably due to excessive woodiness and lack of fertilizer. We just purchased the house last spring…
Hi Ken,
I’m sure the pruning saw should be okay if it makes clean cuts. If you do this in late winter, you may be cutting off the blooms that formed over the summer. I would wait until after the shrub has bloomed, removing old stems that no longer produce leaves as part of the process.
Hello! I have a lilac tree that has been inundated with web worms! The tree now looks dead, although I’m not sure if it is. I was able to remove the webworms from an adjacent lilac tree (it only had a couple and the worms were still in the web) but this one had far too many and I noticed the worms have gone. What should I do for this beloved tree now that the web worms have ravaged it?
Hi Christina, The worms don’t typically cause lasting damage to trees and shrubs. Getting rid of the webs was a good idea and is one of the recommend ways to control them. The tree should bounce back in spring.
Hi I’ve got a fairly old lilac tree that blooms every year. I’ve started cutting off the dead flower heads, but I’ve noticed some of the branches are almost bare with a few leaves at the end. Should I cut off these branches completely? Please help 🥺
After your lilac has bloomed in the spring, you can take out the older canes or stems that are 2 inches in diameter or bigger. Only prune one third at a time.
Do lilac Bushes benefit from being fertilized? Is so, what kind a should I buy?My large bush is three old and had 7 lilacs this year…the most so far, but makes me jealous when I see others like mine that are chock full of blooms.
I don’t generally fertilize my lilacs, but you can add some in the spring when they first start to produce leaves. Also be sure to prune right after blooming so that you don’t inadvertently remove next year’s flowers.
Hello Tara, I have an old lilac that is just not the greatest.
I prune in the spring after they bloom, but I never get many flowers. It’s gotten quite tall, and the top is where the most flowers are!
They don’t even start until where my 5’4 shoulders are!
Now there ARE a lot of shoots underneath. Do I just lop of the top and hope the suckers turn into a bush or just go buy some new bushes? Signed Sad in Ohio:(
Hi Lee,
It’s possible you may need a bigger, more long-term lilac reno. I’ve found some helpful tips in this extension article. https://hortnews.extension.iastate.edu/1993/2-10-1993/lilac.html
Hi there,
I have a huge overgrown lilac tree. The main stem is at least 3” across. I live in Vancouver BC and it is now mid-April. Is it ok to trim out this huge stem and maybe one other now? Lots of suckers coming up too.
Thank you!
Hi Fran, I would wait until after your lilac has bloomed.
Hello. I live in Michigan and just bought a Boomerang Lilac in a pot that looked dead, but the gardening center assured me it’s just dormant. The ground is now frozen. Do I put the pit outside or keep it in my garage? Do I need to water it? Thanks for your help!
Hi Katie, I would probably place it in a sheltered spot in the garden and surround it in mulch. If you get rain and snow throughout the winter, I probably wouldn’t worry about watering – unless you haven’t had any precipitation recently.
We recently got a house with 2 lilac bushes in the front yard. They didn’t bloom this year. A neighbor mentioned that they haven’t seen them bloom in years. They seem very spindly. There’s only leaves at the very ends which makes it look very sickly. Can they be cut back? Is there a chance they might bloom again?
Hi Jennifer,
I feel as though you have nothing to lose if you cut them back. However, keep in mind that if they did somehow form flower buds for next year, you could be removing them if you prune in the fall. You may want to wait until spring, see what the plant does and then decide accordingly.
Hi!
We purchased some lilac plants this year, from a lilac gardens in Southern Washington. They are all growing, 2 have bloomed.
One plant is growing slowly, straight up, with only the main stem. I’m not sure which kind it is, but it has large leaves. Will it eventually branch, or do I need to do something to it?
Thanks for your advice!
Hi Margaret, You can try cutting it back a bit and see if it forms more shoots next year. Know that if you do this in the fall, it likely won’t flower for you next year.
Hi! I have a lilac bush that is much too tall to reach for cutting off the wilted blossoms. The ones I can reach, I have snipped off as directed. The bush is growing by leaps and bounds each year. Apparently, my inability to reach has not stopped it from doing well.