If you want to grow beautiful lilac bushes in your garden, then you’ll need to learn how to prune them properly; think of it as the most important step in your lilac care routine.
Pruning lilacs is the best way to encourage your shrub to produce generous blooms, Spring after Spring.
Now let’s get you comfortable with pruning lilacs!
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Why Pruning Lilacs Should Be a Yearly Gardening Task
If you’ve ever seen a lilac bush in person, you know they can grow several feet tall (sometimes up to 30 feet, depending on the variety you plant) and rather wide.
These bushes can produce numerous shoots that sometimes intermingle, which reduces airflow and sun exposure within the bush- something lilacs need in order to grow well.
These individual shoots can also make the bush less attractive, which is why some people trim them down all the way to the ground before they get out of control.
The biggest problem with forgoing yearly pruning and letting your lilac bush grow wildly is that most of the blooms will grow far above eye-level.
Since lilac bushes are grown for their fragrance, growing them several feet above your head can be a waste.
If you have to look up at a 20-foot lilac bush to see your blooms, then it’s time to prune it down – the right way.
Remember: once you let your lilac bush grow much taller than you, it’s going to be difficult to tame.
It will be far more work-intensive to prune a 15 to 30 foot bush than it would be to prune one that sits at 6 or 8 feet tall.
LILACS – WHEN TO PRUNE
Timing is one of the most important factors in pruning lilac bushes. Once your bush reaches 6 feet tall, yearly pruning should definitely become one of your must-do gardening tasks.
Your lilac bush will reach this height after a few years worth of growth.
Thankfully, when it comes to lilacs when to prune is not a difficult thing to master – you’re basically deadheading the flowers after they’re done blooming.
You should always prune lilacs as soon as your blooms have turned brown, because this means they’re done for the year and will now have to start getting ready for next year’s show.
The best way to tell is by quickly observing the color and texture of the blooms: have the blooms lost their color?
Are they turning brown? Do they feel crispy when you touch them? If you’ve answered yes, then your lilac bush is done blooming.
The blooms will definitely NOT look as vibrant as they did when they started to flower. This lilac bush, for instance, is still flowering.
Since there are literally hundreds of lilac varieties and hybrids, it’s difficult to generalize blooming times.
For instance, some hybrids have been created to thrive in zones that have warmer winters, such as the “Lavender Lady” variety, which can be grown successfully in zone 9 (Yes, that’s you, So-Cal!), and thus has an earlier bloom time than lilacs that are grown in colder zones.
Variety is important because some are categorized as early bloomers (early May, or even earlier in warmer zones) while others are categorized as late bloomers (late May to early June).
You’ll need to keep a watchful eye on your shrub when it comes time to pruning lilacs.
When you see brown blooms on your shrub, you’ll know it’s time to work on it with your pruning shears (I like these shears because they’re inexpensive, get the job done, and have thousands of positive reviews on Amazon.)
What To Avoid When Pruning Lilacs
The biggest mistake you can make with pruning a lilac bush is pruning off new wood because that’s where your plant will grow next year’s blooms.
This is why timing is everything.
If you cut off branches that aren’t spent, your lilac bush won’t produce any flower clusters for you next year.
TIP: It’s better to be conservative than overzealous when pruning lilacs.
Also, don’t pull out your hedge trimmer to do this job.
Hedge trimmers are not ideal for pruning lilac bushes for two main reasons: 1) you might unknowingly cut off next year’s forming blooms while you’re shaping and 2) lilac bushes should hold a round shape rather than a flat-top shape.
PRUNING LILACS AFTER BLOOM
The way you prune your lilac bush will also depend on how you like your lilac bush shaped.
Some people like a wide lilac bush while others prefer to keep their’s shorter and smaller in circumference.
The rule of thumb, however, is to cut off each dead bloom and its INDIVIDUAL flower stem, which is referred to as “old wood”.
You’ll cut right above where the individual flower stem meets the other branches.
This is the most important part of pruning because it will prevent your lilac bush from producing seeds, which would take the plant’s energy away from producing buds that are necessary for next year’s blooms.
IMPORTANT: Lilac bushes start to produce “buds” on the end of new wood stems, which is why you want to prune right after blooms fade and before new growth happens.
If you unknowingly trim off the tips of these branches, your lilac bush will not produce any flower clusters for you next Spring.
Removing Shoots from Your Lilac Bush
If your lilac bush has produced smaller shoots that are growing next to the main trunk, go ahead and cut these down to the ground so you can maintain a neater shape and also promote better airflow within the bush.
You can also trim off any branches that are sticking out from the middle of the bush, which will also promote better air circulation and let more sunlight in.
See those stems growing next to the main trunk, in the photo below? Those are called “suckers”, and those are the ones you’ll want to cut down to the ground.
You should also snip off any branches that are thinner than a pencil, like those shown below.
Also, pull out any weeds that are growing around your lilac bush.
Reinvigorating Lilac Bushes That Are Old or Overgrown
Many people have problems with overgrown lilac bushes that have grown several feet above eye level and have stopped producing flowers.
When this happens, you’ll want to slowly remove 1/3 of the bush’s oldest branches every year because this will encourage the bush to grow new shoots.
Remember: new shoots are necessary for producing flower clusters.
This 1/3 method is ideal because it won’t force you to cut down your entire lilac bush to the ground, something that would leave you with zero chances of blooms for several consecutive years.
Gradually getting rid of older wood each year to promote new growth will still leave you with a lilac bush that produces foliage and (hopefully) a few blooms each Spring.
After you cut off the old stems, new shoots will start to grow out from the bush and in three years or so, these new shoots will start to produce large, healthy flower clusters.
Within a few years, you’ll have an entirely fresh lilac bush that should continue to bloom for you for years and even decades to come as long as you prune annually in the appropriate manner and understand everything else that’s required to successfully grow lilac bushes.
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