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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 a very old lilac tree. It was here when we moved in in ‘86. It is now to the point where the center woods are almost bare and the tree hasn’t bloomed nicely for the past few years. I had my husband take it down to the ground. I’m hopeful I haven’t killed it for good.
Hi my Lilac tree has been very healthy until this year it seams to have been frozen. Our early chinook weather made it start to bud and then we got really cold weather. The tree now has some new growth and some branches go leaves. There are many that are dead. should I trim the whole tree back or just cut the dead branches off.
Advise.
Liat
Hi Liat, for this year, I would just focus on the dead branches and see what comes back next year.
Hi Tara,
I forgot to prune few lilac blushes I have.
they are probably 4 years.
It is summer, they look healthy, however when can prune them?
thank you!
Hi Talia,
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!
Hi Carisa, I’m not sure what variety you have. You can still prune the flowers. The green seeds are the seed pods produced by the flowers. This is what you can trim.
Hi Tara,
I have a lilac tree that has green leaves with veins of white in them. Not sure what kind this lilac is. Any idea? Also it is early July and the blooms have been done for two and a half weeks now. Can I prune spent flowers still? Should I wait till spring now? Also seeing green like seeds on spent blooms, what is this?
Sounds like witches broom. Are the branches long with all the new growth bunched together at the top? If so, it is an incurable bacterial disease and needs to be removed before it spreads to surrounding plants.
Hi Tara,
I have a dwarf lilac tree (I think). It was here when we moved her 6 1/ years ago. I’m trying to become a better Gardner and am wondering about pruning it. I may have waited too long. The tips are brown but when I look under the brown, it’s green. Also there is a gap in the middle of the tree on one side.
I would cut out the dead bits. If it’s recently bloomed, you can prune, but don’t wait until too late in the season as you’ll risk cutting off next year’s flowers.
Hello,
I had a 1 year old lilac plant that was doing great. I had it since it was about 3 inches tall. It grew to about a foot very healthy. I went out to look at it this morning and a squirrel tore it apart. there is still root about i inch down below the dirt. Is there any way I can get that to regrow?
Thanks
Hi Anthony, I’m sorry to hear that. I had a squirrel tear apart a mature lilac to build a nest in my chimney! It did grow back, but it sounds as though I had more left. That said, it is very possible that you’ll get some growth from that root that is still there. At the point, it’s kind of a wait and see scenario…
I bought a Lilac bush 3 yrs ago, it is 5 feet tall right now but it never had flowers. I prune it before winter..does this the only thing wrong I am doing (what I learned from you) or any other thing also. What should I do now so it can bloom next year.
Hi Raaziah,
If you prune it before winter, it’s likely you’re pruning off next year’s flower buds. The best time to prune a lilac is right after it flowers, which is right about now.
We moved into a new house in August 2018 and have two lilac bushes on either side of the house in the backyard. One has produced about 4-5 branches of flowers so far but the other one has absolutely zero flowers. I noticed it didn’t really produce much of anything last year as well. Any helpful insight?
Hi Shannon, have you pruned your lilacs later in the summer?
I have one that is not blooming. Should I try pruning it back and seeing if it will bloom next season.
Hi Wendy, I would try pruning now to see if it encourages blooms next year.