How to Prune Lilac Bushes

Lilac bush with light pink flower clusters on spike next to large leaves

The Spruce / Steven Merkel

Project Overview
  • Working Time: 1 - 2 hrs
  • Total Time: 2 hrs
  • Skill Level: Intermediate
  • Estimated Cost: $0

Most flowering shrubs need regular pruning to keep them vibrant, and the common lilac (Syringa vulgaris) is no exception. You can keep lilacs blooming with very little effort on your part. However, if your lilac bush is out of control, left to grow and spread on its own, it will eventually only flower on the tops of the uppermost branches. Thus, you should prune lilac bushes annually after the first five years to maintain their form and create a balance of new flowering shoots and older stems. Your lilac also might occasionally require a more extensive "rejuvenation" pruning to revive a bush with very thick stems and minimal flowering.

Here's what you need to know about how to prune a lilac bush.


Click Play to Learn How to Prune Lilacs

When to Prune Lilac Bushes

How tall lilacs should be depends on the variety you have. But in general, by the time a stem reaches more than 2 inches in diameter, it should be pruned. If you are diligent with annual trimming of your lilac, the shrub will grow to anywhere from about 8 to 15 feet tall with flowers throughout the branches.

The general rule of thumb is to prune mature lilac bushes just after the flowers have faded in the spring. Lilacs set next season's flower buds almost immediately, so late pruning will mean sacrificing the next year's flowers. For instance, July will likely be too late to prune lilacs if you want to maintain those buds. And you should avoid pruning lilacs in October—or whenever you do your fall garden cleanup—to ensure that you have flowers next spring. Pruning early also gives new shoots more time and energy to develop, so the bush can remain healthy and hardy over winter.

how to prune a lilac bush illustration

The Spruce

Get expert help on all things landscaping

We can't all be experts. Find and compare quotes from top-rated professionals near you.

Get a Quote

The offers that appear in this table are from partnerships from which The Spruce receives compensation.

What You'll Need

Equipment / Tools

  • Bypass pruner
  • Loppers
  • Pruning saw (optional)
  • Stepladder (optional)


  • Mature lilac bushes


Materials and tools to prune lilac bushes on wooden surface

The Spruce / Steven Merkel

Regular Maintenance Pruning

How far you can cut back a lilac bush follows the general shrub pruning rule: Cut no more than a third of the stems each year, starting with the oldest. That will help the plant remain constantly vital, with new stems developing as old stems bloom. Your goal for a lilac pruning diagram is to have a bush with somewhere between 10 and 12 stems, all of them between 1 and 2 inches in diameter.

  1. Prune Unsightly Features

    Begin by pruning dead or diseased stems, pencil-thin suckers that are far from the bush, and twiggy growth. Cut these back all the way to ground level. Pruning shears or loppers will generally handle these stems.

    Red loppers pruning dead stem closeup

    The Spruce / Steven Merkel

  2. Remove Any Stems Thicker Than 2 Inches in Diameter

    This regular removal of entire old stems will prevent your lilac from becoming too tall. Avoid cutting off just the tops of long stems because this can leave the plant with an odd, unnatural shape. With very large stems, a pruning saw might be necessary. Thick lilac stems can be very tough.

    Thicker stems from lilac bush being cut off with pruning saw

    The Spruce / Steven Merkel

  3. Trim Remaining New Stems

    If you want your lilac to fill in more and become shrubbier, trim the remaining new stems to an outward-facing bud. This means pruning just beyond buds that face away from the center of the plant. This technique will cause more branching and create a denser shrub.

    Lilac bush stems with buds and new growth being pruned with red loppers

    The Spruce / Steven Merkel

Rejuvenation Pruning

Older lilacs can have stems as thick as small trees and will flower only on the topmost branches. Fortunately, rejuvenation pruning can revive an old lilac in about three years' time. There are two approaches you can take.

The less drastic approach to getting an overgrown lilac back into shape is to use the "third" rule. Prune a third of the oldest branches all the way to the ground each year for three consecutive years. Start by taking out the thickest stems first. Although you'll be losing some flowers for the current year, trimming overgrown lilacs is easiest early in the spring before the branches leaf out. After three consecutive years of pruning your overgrown lilac in this way, new shoots should comprise the bulk of the plant. The plant will begin to bloom all over, and you can do regular maintenance trimming from that point on.

If you can't stand the look of your old lilac or you just want a quicker approach, you can take the drastic measure of cutting back the entire plant to about 6 to 8 inches above the ground in the early spring. Fertilize the plant with compost or a balanced fertilizer to prompt new growth. New shoots will develop throughout the growing season; let them grow through the summer. The following spring, begin pruning out the spindly growth, and maintain the healthiest shoots while considering the shape of the plant. Encourage branching by cutting back the remaining shoots to just above a bud. Carry on with regular maintenance pruning after this.

Working With Japanese Lilac Trees

The Japanese lilac tree (Syringa reticulata) is a plant that can grow as high as 30 feet and has become increasingly popular in urban environments. It has a vase-shaped crown with spreading branches, and it produces showy white flowers in June.

Consistent with their tree-like shape, these plants should be pruned in the same manner that most small trees are handled. Prune to maintain an open interior and several main branches that form a vase shape. Lilac trees generally require little, if any, pruning until they are a few years old.

After this, any necessary pruning should be done immediately after the flowering period is over. Remove dead or diseased branches, as well as any branches that interfere with the overall vase shape or clutter the interior of the tree. If the lilac tree grows too tall, you can cut back individual branches to around 1 foot below the desired height to prompt dense growth at the top.

Tips for Pruning Lilacs

Dwarf lilacs, such as ‘Palibin’ Meyer lilac (Syringa meyeri ‘Palibin’) and ‘Miss Kim’ Manchurian lilac (Syringa pubescens ssp. patula ‘Miss Kim’), look similar to the common lilac. However, how to prune these lilac bushes differs. They rarely require maintenance pruning, though you can trim when necessary for shape.

Like other lilac varieties, they also can benefit from deadheading. Deadheading is the practice of removing dead blooms from a plant by hand. With some plants, this helps to stimulate continuing blooms.

New lilac plants should begin blooming within two to five years. Deadheading the spent flowers will encourage new bud development for the next spring. However, once the plant has matured, it won't need this encouragement, and you'll likely have so many flowers that the task would be too time-consuming.

As with any plant, some years your lilac will bloom magnificently and some years not so much. Blooms are often dependent on the weather. A pleasant summer during which healthy new growth develops will reward you with abundant blooms the following year. A summer with extreme weather will yield fewer flowers. So don't panic if your lilac isn't as vibrant from one year to the next. As long as the plant is healthy and you keep up with maintenance pruning, the flowers will follow.

Article Sources
The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Pruning Large, Overgrown Shrubs. Iowa State University Extension.

  2. Prune Lilacs Soon After Bloom. Oregon State University Extension.

  3. Pruning Lilac Bushes: Expert Response. U.S. Department of Agriculture: National Institute of Food and Agriculture.