How to Deadhead Lilacs in 7 Simple Steps

Deadheading your lilacs can be one of the best ways to encourage their beautiful blooms. Getting the timing right on when to deadhead is important, but deadheading lilacs is a fairly straightforward process. In this article, certified master gardener Liz Jaros walks through 7 simple steps to deadhead your lilacs this season!

deadhead lilacs

When the much-anticipated garden grown lilac show is over and you’re left with nothing but faded former blooms, you might be tempted to move on and direct your attention elsewhere in the yard. If you’ve timed your garden right, another plant will be flowering soon to fill the sensory void your lilacs have left behind.

Before you go, however, you should take a minute to gaze off into the lilac future. A future where vibrant panicles of pink, purple, and white bounce on the ends of arching branches and fill the yard with the scents of Spring. A future where the lilac display is so dense, you can barely see the leaves behind them.

For lilacs, that future begins with deadheading as soon as this season’s cycle is complete. Since this important maintenance task has such a major impact on the next bounty of blooms, let’s look at 7 ways you can ensure that your best lilacs are yet to come.

Step 1: Know Why You Deadhead

secateurs and trimmed lilac flowers on the grass
Withered flowers are pruned to complete one reproductive cycle and produce more blooms.

Quite simply, deadheading is the process of removing dead or fading blooms from a live plant. Without delving too much into the nitty gritty of pollination and reproduction, a plant’s sole purpose is to complete its reproductive cycle and make more plants. Bright, colorful flowers attract pollinators, which fertilize the ovum, which produces the seed that will then spread and grow.

Since dying flower heads are an indication that seed production has begun, a flower’s growing system will then divert its focus from creating showy blooms to nurturing its roots and foliage. When we remove spent or fading flowers from a healthy plant, we are actually tricking the plant into thinking it should send up more blooms.

Since lilacs bloom on old wood and generate buds for next year very soon after this season’s flowers have faded, deadheading spent lilac blossoms will encourage the plant to direct its energy toward creating bountiful, beautiful buds rather than boring old roots and leaves. 

Step 2: Know Your Lilac Type

Syringa vulgaris
To determine the method of lilac pruning, you need to determine whether your lilac has a tight or loose habit.

With 25+ species and thousands of cultivars, lilacs come in many shapes and sizes. They range in height from 3 foot shrubs to 30 foot trees and feature strong-scented panicles of pink, violet, white, blue, lilac, magenta, and purple in early to late Spring.

Generally speaking, lilacs can be tight and compact in form with small leaves and dense branching structures, or they can be loose and wild with rambling branches and an unruly habit. They also come in tree and shrub-tree form.

Small leaf lilacs (Persian and Chinese varieties), which are often planted in groups or hedges, will have more delicate and numerous flowers, while large leaf (Common or French) lilacs will have larger heavier blossoms that are more spread out.

While it’s helpful to know the exact species and cultivar you’re deadheading (and what its typical flowering time is), it’s not crucial to the task. Take a minute to determine whether your lilac’s habit is tight or loose and it will help guide your deadheading approach.

Step 3: Deadhead After Flowers Fade

faded flowers on the lilac bush
Faded lilac flowers need to be cut off as their root system will not produce new buds.

Timing is everything when it comes to deadheading lilacs. Faded flowers can stay on branch tips throughout the season (some will even hang in there through winter if you don’t cut them off), and since they aren’t really an eyesore, it’s tempting to just let them be. But you really shouldn’t.

Remember that a lilac’s root system considers faded blooms to be a reproductive success and will not be compelled to nurture any more buds, so force yourself to get out there with your tool bucket as soon as the color is gone (and ideally before new buds have formed). You’ll thank yourself next year.

Step 4: Make The Proper Cuts

Cutting with a bypass pruner of deadhead lilac
For pruning lilacs, it is best to use a bypass pruner.

A bypass pruner is the tool of choice for deadheading lilacs. It’s small but powerful, with a very sharp thin blade that slides past a thick blade. For denser, small leaf varieties, some gardeners prefer a florist’s snip or a small scissors.

Whatever tool you select, make sure it’s clean and sharp. Ethanol or isopropyl can be used to quickly remove pathogens from blades. Or use a solution of 9 parts water to 1 part bleach to disinfect tools that have been used on other plants in the yard. Have your local hardware store sharpen anything that’s not going to produce neat, perfect cuts, and always keep tools oiled and stored in a dry location.

Beginning just beneath the base of your lilac’s spent flower, slide your fingers down its stem until you reach either a set of leaves, a new bud, or a side stem. Make your cut just above one of these points. Always aim to perform cuts that are fast and clean, with no breakage or tearing of the stem.

Repeat until you’ve pruned off all spent flower heads (or as many as you have the patience for). Some lilac flowers are very dainty and plentiful, which can make this a tedious task. If you miss a few, don’t beat yourself up. A partial deadhead is better than none.

Step 5: Save or Dispose Old Blooms

cropped lilac flowers on the grass in the garden
After pruning lilacs, be sure to remove dead flowers from your garden to avoid attracting insects and rodents.

Try to remove the deadheaded blossoms from your garden if possible. Leaving them on the ground will encourage insects, rodents, mildew, and other potential problems. But again, if a few blooms fall to the ground and don’t get tossed in your compost basket, it’s not the end of the world. Gardening is not about perfection.

If your lilacs still have some color (and ideally scent) left in them, they can be tied upside down and air dried in a warm, dark room and used in dry flower arrangements. Or they can be pressed in a book for use in botanical frames or the like.

Step 6: Repeat if Necessary

gardener pruning deadhead lilac flowers
If you have a re-blooming lilac variety in your garden, be sure to repeat the pruning process after it blooms.

If you know you have a reblooming lilac variety, be prepared to repeat the deadheading process in a month or so. Even though you’ve done it once in late Spring or early summer, you’ll have to do it again (and with some varieties, a third time) after each bloom cycle is complete. This will encourage the fullest bounty of blooms possible for next season.

Step 7: Know When to Skip it

rejuvenating lilac pruning
In the case of rejuvenation pruning your lilacs, you can skip deadheading flowers.

If your lilac shrub is too tall to safely deadhead, or if you don’t want to shell out for an arborist to cherry pick the spent blooms on your 20-foot tree, you can let it go for a season or two. Your lilac’s bloom production will probably decrease slightly with each passing year, but you’re likely to still get at least a smattering of blooms.

You should also skip deadheading if you plan to perform a rejuvenation prune on your lilac at the end of the season. The technique involves cutting the whole shrub down to somewhere between 6 and 12 inches from the ground, and it will remove all of your lilac’s buds anyway.

Final Thoughts

With lilacs blooming so early in the season (and a gardener’s natural tendency to focus on what’s about to bloom next), it’s easy to forget to deadhead them. But it’s definitely a task worth working into your late Spring or early summer maintenance plan. So put it on the calendar and get out there with your pruners. You may find the process of cleaning them up and looking forward in time to be somewhat cathartic, and you’ll likely reap the rewards with bountiful blooms next year.

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