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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:
I have several lilacs in the yard; two bloomed already this year and have lost all of their flowers, but three of my (very tall) lilacs have feathery – blossom/conical shaped growth, but no flowers. I can’t tell if they are going to bloom or not. It’s been a week and no change. Have you seen this before? Writing this in mid-June from the Catskills, NY. Thank you!
Hi Renee, Is it possible the lilac was trimmed later in the season last year, which might have inadvertently removed spring blooms? Or, if it’s a bit older, perhaps a good pruning this year will rejuvenate the plant and help new growth for next year.
My husband in late March pruned back his grandma’s very old lilac tree to about foot from the ground. It was very large but this past year we noticed shredding and some holes we are assuming borers damage. Grandma did not want to lose tree completely and neither did I. Now that it’s been cut back, what types of care and preventive maintenance should I help her with this. We reside in West Virginia and weather is still unpredictable this time of year. And I do not know for certain what needs to be done now it’s been cut and how to keep borers away and to make sure it starts back over healthy..
Hi Cherie, I’m not familiar with this pest, but this article may be useful. https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/insects/caterpillars/lilac-borer-and-ash-borer.aspx
Hi
I have a lilac bush that appeared of its own accord a few years ago, its not really in the best place. It seems to be mostly suckers with no main stem and blooms right at the top of the stems. I wonder if its best to try and dig the whole thing up? Not sure what’s best to do.
Many thanks
Hi Jackie, Since it appeared out of nowhere, I would try to dig up a stem and see if it does well in another spot in the garden.
I planted a lilacs bush 9 years ago !
No flowers I prune it every year
Hi Deanna, at what time of year do you usually prune? It’s possible that you are inadvertently pruning off next year’s blooms.
Hi. I have two lilac plants, both are lovely, but, the bottom half is just dark and woody, would it benefit from trimming right down?
I would prune out old wood, but if the wood has new growth on top, be careful how far down you prune. Leave some of that new growth.
Hi, I pruned down my dwarf lilac bush, it bloomed repeatedly all summer! Was not sure when exactly to prune so did it yesterday. Will it survive the winter ok?
Hi Nancy, I’m not sure where you live, but it should be okay.
Tara,
I am planning to plant several lilac shrubs toward the end of next month (October), before the ground freezes and I would like to have as long of flowering period as possible in the spring. My understanding is that different varieties bloom at different times, can you tell me what varieties are early, standard, and late bloomers?
Also, I would like to harvest the seeds to try to grow new shrubs. Is there any particular things I should look for on the seed pods to know whether the seeds are mature enough to harvest? Or would letting the seeds mature take too much energy from the parent shrub?
Thanks for your help,
Julia
Hi Julia, Harvesting the flower heads helps the plant to focus on producing flower buds for next year rather than seeds.
Hi Tara Nolan. I have a boomerang. Live 1 hour north of Toronto. It is 3yrs this summer. It is end of September and just noticed the level have brown on them. Almost all the leaves except for the ones near the bottom. It is almost like they were frost bitten. I looked under each leaf and they look healthy and green. Would you be able to explain this to me. Thank you for your time.
Hi Nadene,
We had a very hot, dry summer, so it’s possible that the plant has suffered a bit from the drought. It’s also possible it could be a disease, like powdery mildew or bacterial blight. I would search these and see if the leaf images compare to determine what’s affecting your plant.
We have lived at our house for just over five years. I knew nothing about pruning my mature lilac bushes/trees. They have bloomed every year, except this year. There were a few buds starting but they never developed into blooms. So, the past couple of nights I have been using my hands to get all the dead flowers off from spring. I have seen several green buds so figured it was for next year. Well, I looked in the center and see several branches that have no free leaves on them. Does that mean they are dead and should be cut? I probably have over 30-40 stems coming up from the ground, or base of the tree. There are probably 3-4 trunks at the base that branch out and up. One Bush is fuller and taller than the other one. They both are at least 8-10 feet tall with the fuller bush almost touching the electrical line that runs to the house. I need to shape them, prune them, and cut them back so they look nicer and aren’t so wild. Also, I have lots of suckers all around the sides of the bushes and hanging over the driveway. I hope I didn’t mess these bushes up by taking off the dead, brittle flowers and the brittle dead branches. There are still a lot of branches that don’t have leaves on them period, just a branch with no stems or green sprouts for new growth. I want to make these trees healthier. These shrubs are probably 10-15 years old. Of course, that’s a guess. I know they are at least 8 based on pictures on the city’s website. Anyway, please, help me or direct me to some resources. I really don’t have much of a green thumb, so to speak. Thanks in advance!
Hi Jennifer, It sounds like you’ve done a good job of pruning. It’s okay to clip out the suckers, old blooms, and dead branches. If you’re looking for more care info, I would check with an arboretum or master gardener extension. Here’s one I found from Cornell. http://chemung.cce.cornell.edu/resources/lilacs
Hi I have a very tall lilac I decided to cut it down to about 6ft today did I make the wrong move and not have flowers in the spring?
Kind regards
Carl
Hi Carl, It’s possible that you may have removed some blooms, but anything below the six feet may have buds waiting for spring.