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Pruning 101: How to prune Lilacs

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How to Prune Lilacs

Annual pruning of lilacs is essential for the development of a robust framework of stems and to promote vigorous growth, which in turn enhances flowering. The pruning process involves cutting back diseased, misshapen, and unproductive stems to the ground level. Additionally, thinning and removal of some stems are necessary to encourage properly spaced and vigorous growth.

To prevent overcrowding, new shoots that arise from the roots are trimmed, leaving a few inches between each stem. Pencil-thick shoots are retained as they are the most productive, while small, twiggy growth is removed as it is unproductive and may indicate too much shade or too many old, nonproductive stems. Stem removal can be done immediately after flowering or in late winter, sacrificing a few blossoms. It is recommended to cut off shoots and stems at or just below soil level.

If you know how to prune Lilacs the right way, it will help you maintain their appearance, keep them healthy, encourage new growth, and reward you with magnificent blooms. Read on to learn about the proper techniques for pruning lilacs!

The basics of Lilac pruning

Pruning is a familiar practice to any experienced gardener, as most plants benefit from it. If you’re new to gardening, you’ve got nothing to worry about! Pruning is the selective removal of plant parts such as leaves, stems, and branches – the process is pretty simple when you understand it!

Regularly pruning lilacs promotes their health as it helps to avoid pests and diseases, improves air circulation, and encourages new growth. As a result of enhanced health, you’ll see rich blooms.

What tools do you need?

These are the few basic things you’ll need to get started:

  • Pruning shears. Pruning shears are essential for making clean cuts on stems and smaller branches.
  • Loppers. Loppers come in handy for thicker branches as they provide larger leverage.
  • Pruning saw. A pruning saw isn’t always necessary for lilac pruning. However, you might need it for large or overgrown bushes.
  • Gloves. A pair of gardening gloves protect your hands from the rough bark.
  • Sanitizing solution. Don’t forget to sanitize your tools before using them and between the cuts.

When to prune lilacs?

It’s essential to prune lilacs at the right time. The optimal time is right after the plant finishes flowering in late spring or early summer. While the pruning should generally take place in May or June, the exact time depends on the climate the plant is growing in and its variety. Pruning immediately after the bush flowers allows it to develop new growth and flower buds. Doing it later in the year can hinder the growth and bloom of the lilac. While pruning lilacs once a year is enough, you can cut off any damaged or dead branches whenever you notice them.

How to Prune Lilacs – the proper Techniques

Selective pruning

There are several methods for pruning lilacs. Selective pruning helps achieve a desired shape and size and maintains the plant’s overall health. It benefits the plant by enhancing airflow, maintaining its appearance, and promoting new growth.

  1. Remove some older branches at the base of the plant.
  2. Locate any branches that are damaged, crossing, or growing inwards. Cut them above a healthy node.
  3. Select the branches you want to remove to achieve your desired result.


The removal of spent and faded blooms is called deadheading. Getting rid of the old flowers prevents diseases and allows the plant to use its energy for continuous flowering and new growth. 

  1. Deadhead your lilac after it has finished flowering. 
  2. Cut off the spent and faded flower clusters below the base and above a healthy node.


Shaping is handy for creating an aesthetically pleasing shape, as you can guess from the name. It also helps to control the size of the plant.

  1. Decide on the shape and size of the bush you want to achieve.
  2. Trim the branches selectively to get the result you’re looking for.
  3. Adjust the growth over time to maintain the shape.


Rejuvenating involves removing a large part of the old wood to promote new growth – this technique works for old and very overgrown bushes. It can stop your lilac from blooming for a few years but pays off in the long run.

Unlike deadheading, selective pruning, and shaping, rejuvenating is done in the winter when the plant is dormant.

  1. Cut the entire bush back to near ground level. Leave it around 8 inches tall.
  2. Select healthy and strong shoots for forming a new framework the following winter.
  3. Trim the selected shoots above a node. Remove all the other shoots to ground level.

Caring for lilacs after pruning

Proper aftercare is crucial for your pruned lilac to thrive. Caring for those plants is simple when you’re aware of their preferences.

Surprisingly, established lilac bushes don’t need watering as their roots go deep enough to seek their water. However, watering is essential during the first few years and over dry spells. Monitor the plant after pruning and provide water when the soil is dry.

A layer of mulch around the base helps to conserve moisture and maintains an even soil temperature. It also suppresses weeds.

While lilacs don’t need fertilization after pruning, they benefit from it in early spring when active growth begins.

And remember to keep an eye on your plant to monitor it for any signs of pests or diseases and adjust care when needed.

Mistakes to avoid

Pruning Lilacs

Knowledge of common mistakes helps to prevent them from happening in the first place. The two most common issues are pruning at the wrong time and over-pruning.

  • Avoid over-pruning by sticking to light trimming. You can always prune off more branches if you’re not happy with the appearance of your lilac once you’ve finished pruning it. Don’t cut off more than a third of the bush – this applies to most plants!
  • Pruning too late in the year is risky as it can affect the growth of the lilac, and the bush may not bloom the following year. Avoid that by pruning your lilac right after it blooms in late spring or early summer.

To sum it up

Properly pruning lilacs enhances their overall health and appearance resulting in vibrant blooms. Applying the tips and simple guidelines in this article will leave you with a healthier and stunning lilac bush, whether you’re a new gardener or a seasoned expert!

Frequently Asked Questions

How to prune miss kim lilac?

Pruning miss kim lilacs is slightly different from pruning most other lilac varieties. It doesn’t require much pruning because of its compact size. Deadhead it annually and regularly monitor it for any damaged or dead branches. Trim the bush when it outgrows its form.

How and when to trim lilacs?

Prune lilacs in late spring or early summer when they’ve finished flowering. Remove spent blooms and selectively prune older stems near the base.

How to prune lilacs in the spring?

Remove spent blooms when pruning your lilac in the spring. Selectively trim older stems near the base and any other branches to achieve the desired shape. Prune right after the plant finishes flowering.

How far can you cut back a lilac bush?

Don’t cut back more than one-third of the plant. Avoid severe pruning.

Can lilacs be cut back hard?

No, don’t cut lilacs back hard. That can affect the blooming of the bush for years to come.

Do you cut off dead lilac blooms?

Yes, cut off any dead flowers – this practice is called deadheading. Doing so helps the plant to direct its energy towards new growth and to prevent diseases.