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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 am a new gardener. I got a house Last year. We have to lilac trees that bloomed this year. But not until the flowering I noticed the trees had a lot of dead wool and old blooms that were never pruned from last years. So, I pruned/cut back a lot of the dead wood that also had some new growing in them. I wish I read this before. That old lilacs might need to be pruned in a three year period of time. I did it all at once today. What does this mean to my two lilac trees? Did I ruined them forever?
Hi Daniela,
It’s okay to prune out the dead wood, and after they bloom is a good time to do it. I’d say your lilacs will probably be just fine.
Hello,
New gardener, and new homeowner here. The previous owner has a gigantic lilac tree/bush (honestly its so big im unsure) it does flow over the roof top (one story ranch) and into neighbors driveway. I did not prune last year as i know basically nothing, and still learning tips and tricks. The neighbor said she has pruned her side for years and they are nice so i dont mind. The neighbor side bloomed beautifully this year. The side facing the yard, not so much. Majority (i would say over 50%) of the yard side seems to have no life. There are several bases to it. Over ten trunks from the ground. Is it safe to cut back all of the dead branches, or should i still stick to the 1/3 rule. Im afraid i will kill it and the previous owner is a family friend would not be so happy, nor would my neighbor who loves it, or me because I like it as well and would like to maintain it. Also i noticed on the yard side, the roots seem to be showing, should i add dirt as well?
Hi Crystal,
It’s okay to cut out any dead wood from the tree. This will also help with air flow. If roots are showing, I would cover them with fresh soil.
We have a lilac tree which has bloomed on a few branches but the the other branches either have no leaves or flowers or withered leaves and flowers . Should we prune and if so how much. Can you give us some advice. Thanks
Hi James, Once the blooms have died, I would prune off anything that seems dead or diseased. The leaves curling could be powdery mildew. A little thinning, even of healthy branches, will help to ensure there is airflow through the shrub.
My 4 yr old bush branches cant support the blooms. Should I feed something in particular. It is @5 feet high and not dense at all
Hi Nanett, Mine drooped under the weight this year, too. Do you prune your lilac?
M lilac has to be more than 10 years old and I have blooms for the first time. May I cut the blooms and bring them into my house? Or should I leave them alone this year? Thank you.
Thank you for clearly stating how I should take care of my brand new lilac bush. I’ve checked several websites but no one was as clear and specific as you were, and I’m now sure I can *properly* care for one of my favorite flowers.
We are finally getting to relandscape my front yard and I have a lilac bush that is in need of trimming. Since it’s September should I wait until March or can I cut it back now. This year it did not bloom anyway due to being neglected for so long. If I cut it back now will it kill the whole plant? I’m not to concerned about gaining blooms right away, mostly just making it healthy again.
Hi Sara,
You can remove any dead or diseased wood now, but early spring is the best time of year to prune a lilac bush (if you’re not waiting until after it blooms).
Hi! I have a bloomerang lilac tree and I pruned it tonight. I think I may have pruned new buds by mistake (new Gardner here). Did I ruin the tree from forever blooming again?
No worries, Emily. If you pruned new buds off, new ones will grow back. 🙂
Perfect timing! Mine have just started to bloom and they are also getting too high.
Happy pruning!
I have a lilac bush that is plentiful on one side and pretty open on the other side. It is about 8 years old and needs pruning. How should I proceed?
I’m guessing the open side isn’t blooming. A good rule of thumb when pruning lilacs is not to prune more than one third of a shrub’s stems per year.
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.
Have you any suggestions for a lilac that loses its colour? I have inherited a lilac bush that bloomed prolifically this spring, but the blossoms quickly faded from purple to washed out cream. Is there something I can add to the soil to help it regain its colour?
Hi Julie, Have the blooms faded like that in previous years?
Tara, this has happened to our bushes as well….Very pale petals, and they hardly lasted 2 weeks (though it was very windy this past month!) I’m a big pruner, but misunderstood the lopping off the flowers when they’re done (I assumed they seeded for the next year)…so thank you for explaining that so well! Also, we do have quite a few suckers…I kinda like them for the green coverage (we have chickens who enjoy foraging with the protection) But I do thin the branches every year, and trim out the little, non-producing twigs so it doesn’t look so woody. A lot of our surrounding neighborhoods have big, even huge lilac bushes! It’s super obvious that none of these homes prune them… And their flowers are so vibrant, and so plentiful!! It’s been probably 3 years since we’ve had such blooms on our lilac… I do not fertilize at all, because of the chickens. And I don’t overwater, either… Our yard is a gorgeous oasis, And everything seems to grow super well for us! I’m just not sure why our lilac blooms have been so lackluster the past couple years… Thank you for any input! I really loved this article!