When And How To Prune A Lilac Bush Like a Pro

Written by Ivy

Jan 29 2023

When And How To Prune A Lilac Bush Like a Pro

Common lilacs (Syringa vulgaris) are a favorite landscape shrub here in Flowers that bloom in the springtime bring beauty and an undeniable fragrance to Ohio and beyond. While other lilac cultivars have different habits and uses in the landscape, they all produce the same spectacular display of flowers that we all adore. Knowing when and how to prune your lilacs is crucial if you want to guarantee that you get the most blooms each year.

When to Prune Lilac Bush


It's crucial to know when to trim lilac bushes. Until they are about 6 to 8 feet (2-2.5 meters) tall, the majority of lilacs don't need to be pruned.) tall. Lilac bushes should be pruned as soon as the flowering is finished. As a result, new shoots have plenty of time to grow for the upcoming blooming season. Lilac buds can be killed if they are pruned too late.

Early in the spring, just after your lilac bush (Syringa vulgaris) has finished blooming, is the ideal time to prune lilac bushes. Lilacs flower on "old wood," or last year's growth. The most flowers will result from pruning immediately after they bloom because new buds will start to form on these branches in mid-summer.

All lilacs should, as a general rule, be pruned as soon as the spring blooming season is over. Pruning later in the summer or fall will result in cutting off most or all of the flowers from the following year because lilacs set their flower buds for the following year immediately after the current year's flowers have faded. This rule of timing applies to the larger common lilacs as well as the cultivars that are shorter or more "shrub" like. While the "when" of pruning lilacs is fairly straightforward, the "how" gets a little trickier. Lilac pruning can either be maintenance pruning or rejuvenation pruning, so let's keep things straightforward for the time being.

How to Deadhead a Lilac Bush

Deadheading is the process of removing spent flower heads from stems to make room for new growth the following season. As part of routine annual maintenance, lilacs should be deadheaded each spring. It's time to start trimming when the flowers start to fade and die.

  • Locate your spent flower, and find the first pair of leaves or a significant side branch to cut back to.
  • Use pruners to cut dead flower heads off at the stem back to the pair of leaves or significant side branch. This promotes the flowers for the following year.

How to Remove Suckers

Suckers are the fresh growth (stems) emerging from the soil. If they are not connected to the shrub's main branch, you can tell these are suckers. During your annual pruning, remove any suckers you don't want to keep because they'll grow into flowering stems in the future and increase the volume of your shrub.

  • Cut off any unwanted shoots that are growing from the ground, as these will draw energy from the rest of the plant.
  • Try to cut as close to the ground as possible so no shoots stick out.

You might want to keep the suckers if you want more than one lilac bush. Propagating is the process of removing these suckers and replanting them. Growing a new plant by using an existing one's vegetative parts is referred to as propagating. Cuttings, root sprouts, layering, or cleft and bud grafts are frequently used methods.

This can help you grow more lilac bushes or other flowering shrubs without having to spend money on buying new ones.

How to Thin a Lilac

Trim stems that are expanding inward, toward the inner branches, to increase air circulation.

  • Remove any branches that are sick, diseased, or weak.
  • Cut any crossing branches that rub against other branches.

Because of this, the shrub will receive more light. If additional trimming is required, do so, but try to avoid removing more than one-third of the plant each year.

Pro Tip: Cutting back to a larger, stronger side branch can help you reduce the height of your lilac bush if you're trying to make it smaller.


How to Maintenance Pruning

Regular pruning can simply include any shaping you choose to do along with the removal of dead, diseased, or broken stems for any lilac shrubs that have not outgrown their space or are still producing vibrant flowers every year. You can also prune your lilacs' spent flowers to promote a neater growth pattern and appearance. Shearing is never preferable when performing this kind of pruning by hand. Try to cut back to an outward-facing bud when making cuts. Hedge shears do not provide as good of pruning cuts as a good pair of hand pruners do.
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How to Rejuvenation Pruning

You may be familiar with their overgrown, unruly habit when left alone if you've ever had an older common lilac in your landscape that went unpruned for many years. Many people mistakenly think that this is the end of the flowering season for these shrubs. In many cases, the upper parts of the shrub—where the plant has grown to a greater height and is exposed to sunlight—are the only places where flowers are actually produced. We're frequently left staring at bare, woody branches at eye level and below once they've reached this stage. For these overgrown shrubs, we can remove entire older canes or stems that are 2" in diameter or larger to encourage a rejuvenation of the shrub. When performing this type of pruning, we want to follow the rule of thirds: remove about a third of the older canes or stems every year for three years. This gives the shrub a chance to gradually change back to a fuller, shorter shrub with more new growth filling in from the bottom. A little extra care, such as fertilization and watering, will be necessary to promote new growth if you choose to drastically prune the shrub the entire way rather than just a third of it all at once. Note that this "all at once" approach is generally not recommended for the health of the shrub.

Although there are many factors that can affect your lilac flowers, including temperature, soil quality, even disease and insect issues, proper pruning goes a long way in ensuring they put on a great show each spring. And don't forget that your dedicated Russell Tree Experts arborist is only a phone call or email away if you have specific questions about pruning or anything else tree and shrub related.


FAQ About Lilac Bushes

Can You Prune Lilac Bushes in the Fall?

In the late spring rather than the fall, lilac bushes should be pruned. Lilacs frequently fail to bloom in the spring because of fall pruning, which removes the majority of new buds. The best time to renovate your shrub is in late winter or early spring.

How Do I Prune An Overgrown Lilac Bush?

You might want to think about cutting the overgrown bush to a height of 6 to 12 inches, depending on how bad it is. This is called renovating your lilac bush and it involves cutting all of the branches down in order to help encourage new growth that can be more controlled.

When a shrub has large, overgrown branches that are at least 12 feet tall and has not received regular pruning, renovation can help. You can more easily control the shape and size of the plant as it grows by chopping the branches down. For it to begin blooming again, though, it may take a few years.

In the second year, you ought to start noticing significant growth, and in the third year, the majority of shrubs ought to begin to bloom. Deadheading on an annual basis is advised at this point.

Another less severe approach is the thinning method of taking off the bigger, older branches. Remember that you should only prune a third of the bush per season, so depending on the lilac, this procedure might take two to three successive seasons. Before proceeding to thin out the middle section, you should trim the larger branches to a height of 6 to 12 inches off the ground.

Look for any dead or damaged wood in the center that might harbor a disease. Eliminating those branches and any branches that are crossing one another should help your lilac shrub look better and promote airflow.

How Far Back Can I Cut a Lilac Bush?

During the remodeling process, you can remove material up to one foot from the ground. The majority of seasonal pruning should be much less. When cutting a branch or limb, you should typically try to cut back to another branch or to 6–12 inches from the ground. This technique enhances the bush's aesthetic appeal while assisting in the prevention of disease in the shrub.