How and When to Prune Lilacs for Bigger Blooms
Lilacs: The Regal Blooms of Spring
Big, beautiful and fragrant flowers makes the lilac one of the most recognizable and well known of the flowering shrubs. Blooming in spring with a burst of color and filling the air with their floral scent, lilacs are one of the first plants to awaken in the garden after the long winter.
Lilacs are hardy, long-lived plants that are easy to grow. Healthy and well-pruned shrubs bloom proficiently in late spring, filling the garden with their sweet scent and color that attract the attention of hummingbirds, bees, butterflies and gardeners. While purple flowers are the most common colored blooms, horticulturalists have developed many different cultivars with flowers in white, pink, yellow and burgundy.
My grandfather loved growing lilacs. His pride and joy was a robust plant that exploded with white flowers every spring. Thanks to his gardening skills and generosity, I have several plants growing in my yard that are the direct descendants of his prized plant. My grandfather is gone now, but I am reminded of him every spring when 'his' lilacs are in full bloom. Thank you, Grandpop!
How to Grow Big, Beautiful Lilacs
Lilacs are a landscape staple for several reasons: they are easy to grow, they bloom proficiently and even after the flowers fade, the shrub looks good in the landscape.
- For optimal blooming performance, select a planting site that receives full sun. Fertilize in early spring with an all-purpose 10-10-10 fertilizer. Reapply the fertilizer again after the blooms fade.
- Established plants are very hardy but newly transplanted specimens may require watering during periods of drought.
- Lilacs are easy to propagate from the many new shoots that sprout from the base of established plants each spring. Use a sharp spade to dig down and around the shoot, creating a small root ball while severing the shoot from the parent plant. Transplant the new little plant into a sunny location and keep it watered well until it becomes established.
If these blooming shrubs have any drawback, it's that their flowers tend to fade quickly. By planting several different varieties with different flowering times in early, mid and late spring, gardeners can extend the blooming season. Careful and selective pruning helps to keep a plant healthy and will increase blooms for the following year, but pruning a lilac incorrectly or at the wrong time can reduce or eliminate those wonderful spring flowers.
Here are a few tips for pruning lilacs to get the most blooms every year.
When to Prune Lilacs
- There is a right time of year to prune a lilac, and there are also lots of wrong times for pruning these flowering woody shrubs. They grow quickly and they can grow quite tall so they need an annual trimming to retain their shape and to keep them blooming consistently every year. The only right time to prune these shrubs is just after the last of the flowers fade away in late spring. Prune lilacs in late spring to remove the dead flowers and broken or damaged limbs before the plant sets out its buds as it prepares for next year's blooms.
- Deadheading the spent blooms and removing the spent flowers also prevents seeds from developing for the next generation. Deadheading redirects the plant's energy towards producing those new buds that will form the flowers for next spring. Removing the old flowers is an important step towards ensuring that your shrub will bloom profusely year after year.
- Lilacs begin to form next year's buds shortly after this year's flowers finish blooming. To avoid cutting away next year's flowers, it is very important to trim them right after they finish flowering. The new buds are hard to see, but they begin to form in the late spring. The trick is to prune and shape the bush within the first few weeks after the plant finishes blooming, but before it starts growing new buds. Waiting too long to trim your lilac means either putting off the chore until next year or risk cutting off the flowers for next spring before they even get the chance to grow.
How to Prune a Lilac Properly
A well-shaped lilac needs annual pruning to retain the rounded form that most gardeners desire. Pruning is also important for controlling the overall height of the shrub. Depending on the variety, these hardy growers can reach up and over 20 feet in height. And since most of the buds form on the tips of the branches, the flowers of a tall lilac will bloom near the top of the plant—out of reach and perhaps beyond where the flowers are easily seen and enjoyed.
- While your plants are blooming this spring, look closely at the shape of the shrub. Also, take note of where the plant is sporting most of its blooms. Lilacs flower at the tips of its branches; the areas that receive the most sunshine will boast the biggest and brightest flowers.
- After the blooms fade and die off, selectively prune the branches to control the height and to re-form its shape. In most cases, lilacs do not require much pruning beyond deadheading and removing a few select branches to improve the shape and appearance of the shrub.
- Healthy lilacs sprout new suckers from the ground each year. Prune out some of the suckers, and remove any crossing branches or leggy limbs. Remember that they flower on the older stems, making it important to remove only those limbs and branches that are necessary to maintain a nicely shaped and well proportioned shrub.
- Over time and as the plant ages, the interior may become congested with a tangle of older limbs. Lilacs will bloom reliably for years with minimal care, but some older plants may become less productive. To reinvigorate an older plant and to encourage more blooms, remove about one third of the plant each year by cutting the selected shoots and branches back at ground level.
- Severe pruning encourages new growth but since lilacs flower only on old wood, it can take several years before the lilac blooms proficiently again after a severe pruning.
What Is Your Favorite Color of Lilac?
What Is Your Favorite Color of Lilac?
Will Lilacs Grow in Your Garden?
USDA Plant Hardiness Zone Map
The USDA Plant Hardiness Zone Map is now interactive: Search using your zip code or click on your state to find your exact plant hardiness zone for your area.
Will You Have Lilacs Blooming in Your Yard This Spring?
The Right Pruning Tools for Lilacs and Other Shrubs
Spring involves lots of yard work including shaping and thinning out the shrubs, pruning and limbing up trees, cutting out dead and broken branches damaged by the ice and snow, as well as working on a list of new spring projects.
Using the right tools makes pruning a more enjoyable task. Sharp, quality tools not only makes the job easier, but sharp blades slice cleanly for cuts that heal quickly.
The three tools that I use for nearly every pruning job are...
- the bypass shears for deadheading spent blooms and clipping off the ends of thin branches,
- long handled loppers for reaching deep into the shrub and for cutting through thicker branches,
- and a pruning saw for limbs and clearing out dead wood.
The bypass blades on shears and loppers cut cleanly through live branches with very little effort. A pair of bypass shears slice cleanly for collecting fresh flowers, as well as making quick work of nipping off spent blooms. The long handles on give plenty of reach for thinning out shrubs, limbing up trees and reaching deep into the brambles for cutting shoots off at the base.
The lopper's cushioned handle grips are comfortable and slip-free, and the bright orange label helps the tool standout and made it easy to find when I carelessly left it on the ground. The long handle length also gives the tool some extra leverage for slicing through branches.
Bypass loppers are designed for pruning and cutting live branches up to 1-1/2" thick. They are not designed to cut deadwood, which is extremely dry and hard and can damage the cutting edge or even bend the blade. For old dead wood, use an anvil style cutter. If you trim a lot of shrubs and trees, you need both a bypass cutter for living branches and an anvil cutter for dead wood.
A Pruning Saw
For larger diameter branches, the aggressive teeth of a pruning saw rips through wood quickly and with little effort. I use a folding pruning saw so that I can safely close the blade for carrying around the yard.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
Questions & Answers
I have a lilac tree next to the house. It has grown and is now hitting the house and gutter. When is the best time to cut it back? I'll need someone to do this. Will a tree trimmer know how to trim and shape this tree?
Planting shrubs and trees too close to the house is a common problem. It sounds like your house is at risk from the overgrown lilac, and the plant should be pruned so that it will not cause any damage to your home. Most licensed arborists can prune your shrub correctly, but be sure to ask the trimmer questions about how they suggest pruning your lilac.Helpful 9
I have two lilac bushes; both are about three-years-old. One has doubled in size and flowered the year before last with only one set of blooms. It skipped blooming last year. This year, only one branch produced flowers. The other bush has never produced flowers. I have fertilized both each year. What can I do to encourage both to produce more flowers?
Lilacs are usually reliable bloomers, though there are a few possible causes for poor flowering. I've read that they don't like high levels of nitrogen, which is found in most plant fertilizers. I don't fertilize mine at all. Lilacs also like light, and should have six to eight hours of sunlight. Proper pruning is also important, to avoid trimming off next year's buds.Helpful 6
What will happen if I did not prune my lilac last fall?
Lilacs will continue to bloom without pruning. However, pruning helps to control the height and shape of the shrub, and helps to keep them blooming consistently every year. Proper pruning and thinning also helps to increase air circulation; promoting new growth for a strong and healthy plant.Helpful 6
I have a small lilac bush that has one side full of blooms and the other half all leaves. What do I do?
This is an interesting situation, and there may be several contributing factors. Was the lilac pruned last year, and were these limbs trimmed after the buds started to set? Is the leafy side of the shrub shaded more than the flowering side? Or if this is a young shrub that is just starting to flower, the plant may naturally set more blooms next year.Helpful 5
When is a good time to prune my lilac bushes?
Lilacs are hardy plants that can withstand pruning at just about any time. However, you should not trim away more than one-third of the bush per year.Helpful 4
© 2012 Anthony Altorenna