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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:
Hi Tara, I bought a house last year and there was a massive lilacs. I pruned it (maybe a bit too aggressively) right after it bloomed. There was also a million shoots everywhere. I pulled roots for days, trying to get the root system out as much as possible. Some times I had to cut them as I couldn’t get the roots out. I was then gone for about a month and came back to a million new shoots everywhere. Some of them are starting to get into my raspberries and some even crossed under a garden bed and started to shoot out in my grass. I really don’t wanna have to pull roots for days twice a year… I was thinking to maybe use round up on the shoots but worried it might kill the actual lilac trees. Unsure of the ange of those lilac trees, but they were probably close to 20 feet tall befits I pruned them. It was so high I could barely pick anny of the lilac flowers.
Any suggestions to deal with the shoots?
Would round up kill the trees and perhaps the raspberries too?
Thank you for any advice you may be able to provide
Hi Caroline, I would not recommend using any type of chemical herbicide in general, but also it might affect your raspberries. And if they did grow, you probably wouldn’t want to eat them. I usually cut the shoots at the soil line with pruners. That might be quicker than pulling them all out. Unfortunately lilacs do throw up suckers as they continue to grow.
Happy summer!
We have a lilac hedge that is about 50 years old. We trimmed it to within 6″-8″ of the ground last week (after blooms dried up). It’s the second time we have taken it to the ground in 30 years because it grows 15′ high! How/when do I fertilise it to encourage healthy growth next year?
Hi Sherry, The best time to apply a fertilizer (10-10-10) would be early spring when there are signs of fresh growth.
I have a lilac bush that I did not prune last year. So I literally have a couple of new flowers this year. How do I ensure new flowers for the following year?
Hi Jusi, There are a few reasons why a lilac may not flower. There could be too much shade, too much nitrogen in the soil, a sudden freeze in the spring, etc. If it’s an immature bush, it could also take awhile to bloom. I would assess the planting site and soil to see if any of the above issues could be the cause.
Hello love lilacs but never done anything with them until reading your advice. I have a very tall 8ft lilac thats 4ft wide. I trasplanted it a month ago during non freezing weather to a spot that will give more sunlight as it was next to the house and was only getting 5 hours of sun. Its March 3rd and see little seed shaped growth on the tips of branches, no leaves yet. Is it still early enough to cut back and how exteme can I get or should I waite till after blooming, usually mid to late May? Many thanks ahead of time for your site and very welcomed advice.
Hi Dan, If you prune your lilac now, you risk cutting off any spring blooms that have formed. I would wait until after it has bloomed to do your next trim.