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When should i prune my lilac bush


Russell Tree Experts — When and How to Prune Lilacs

Please note: This article was originally published on 4/6/2020 and was republished on 6/9/2021.

Common lilacs (Syringa vulgaris) are a favorite landscape shrub here in Ohio and beyond, with flowers that provide beauty and an unmistakable fragrance every spring. Other cultivars of lilacs offer different habits and uses in the landscape, but provide the same display of flowers that we all love. In order to ensure you get the most flowers on your lilac year after year, it’s important to know when and how to prune them.

When To Prune

As a general rule for all lilacs, they should be pruned immediately after they’re done flowering in the spring. Since lilacs set next year’s flower buds right after the current year’s flowers have faded, pruning later in the summer or fall will result in cutting off many or all of next year’s flowers. 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. To keep things simple for now, we’ll think of lilac pruning as either maintenance pruning or rejuvenation pruning.

How To: Maintenance Pruning

For any lilac shrubs that have not outgrown their space or are still producing vibrant flowers each year, regular pruning can simply consist of any shaping that you choose to do along with removal of dead, diseased, or broken stems. You can also remove spent flowers from your lilacs to help encourage a cleaner growth habit and appearance. It’s always better to do this type of pruning by hand, rather than shearing. When making cuts, try to cut back to an outward facing bud. A good pair of hand pruners is the perfect tool for this and makes for much better pruning cuts than hedge shears.

How To: Rejuvenation Pruning

If you’ve ever had an older common lilac in your landscape that went unpruned for many years, you’re probably familiar with their overgrown, unruly habit when left alone. Many people mistakenly believe that these shrubs have stopped flowering at this point. Oftentimes what’s actually happening is the flowers are being produced on just the upper portions of the shrub where the plant has reached a taller height and is exposed to sunlight. Once they’ve reached this stage, we’re often left to stare at bare, woody branches at eye level and below. 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. We want to apply the rule of thirds when doing this type of pruning - Remove approximately one third of the older canes or stems each year for 3 years. This gives the shrub a chance to slowly transition back to a fuller, shorter shrub with more new growth filling in from the bottom. If you decide to drastically prune the entire shrub this way all at once rather than just a third of it, a little extra care like fertilization and watering will be important to encourage new growth. Note that this “all at once” approach is generally not recommended for the health of the shrub.

Your lilac flowers can be influenced by many things, including the temperature, soil conditions, even disease and insect problems, but proper pruning goes a long way to ensuring they put on a great show every spring. And remember, if you have specific questions about pruning or anything tree and shrub related, your dedicated Russell Tree Experts arborist is only an email or phone call away.

*New* Video!


To accompany the above article, Walter Reins demos how to prune lilac trees in this new video! Click below!

How to Prune Lilac Bushes

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.

    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.

    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.

    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.

How to Grow and Care for Lilac Bushes

Lilac pruning.

Basic Rules and Tips Photo Flickr.com

Tips, Care Views: 60 342 0

Lilac belongs to shrubs for which correct and timely pruning is extremely important. She cannot be neglected.

This article is a continuation of material "Rules for planting and caring for lilacs" .

Sanitary and shaping trim

Sanitary pruning is best done in early spring (March - early April) and in summer immediately after flowering. However, if it was not possible to hold it in the spring, then one summer one will be enough.

In the spring, you need to remove all broken, damaged, frostbite (may form even in winter-hardy varieties, if there were strong temperature changes) branches during the winter. It is also necessary to cut off the shoots that have grown under wet snow in early spring.

Last year's growth is also removed if it is not necessary for propagation by layering: a large number of growth takes moisture and nutrition from the main plant, and also increases the size of the bush and worsens its appearance.

In spring we do not recommend trimming lilacs in height and doing formative pruning: there is a risk of removing flower buds located on the top of the shoots.

Formation pruning, as a rule, is combined with summer sanitary and carried out after flowering. The measure includes:

Do not forget about the newly appeared growth, which also needs to be cut out.

[stextbox id="info" caption="Advice" ccolor="000000" bgcolor="F4B0FF" cbgcolor="F4B0FF" bgcolorto="F4B0FF" cbgcolorto="F4B0FF"]After sawing off large branches, cover the cut with garden pitch. So you prevent the defeat of plants by infectious diseases.[/stextbox]

Rejuvenating pruning

This type of pruning is relevant for aging native-rooted lilac bushes, both varietal and specific. If there are already few shoots on the old branch, then cut it down to the ground. Within 2-3 years, replacement shoots will form from the young shoots.

We do not recommend replacing all the old skeletal branches at once. It is better to do this gradually, 1-2 branches per year. Thanks to this, the plant will rejuvenate without losing its decorative effect.

On grafted lilacs, rejuvenating pruning is carried out up to the trunk above the grafting site. An insulating material, such as garden pitch, is applied to the cut site.

Pruning to regulate flowering

Lilacs have a peculiarity - if one year it bloomed too abundantly, then the next year the flowering will be very weak.

For this reason, regular pruning is necessary to ensure even annual flowering of the bush. It is carried out in early spring, before the start of the growing season. At the same time, part of the shoots with an excess number of flower buds is removed.

Common lilac ‘Beauty of Moscow’

Pruning of faded inflorescences

This type of pruning is needed for laying next year’s flower buds on lilacs.

If faded panicles are not removed in a timely manner, then the nutrients of the plant will be used for fruit ripening, and the number of new flower buds will decrease significantly.

Never break or pluck out faded panicles. They only need to be trimmed, leaving small stumps.

Cutting for bouquets

Cutting flowering branches also activates the emergence of new flower buds. However, they should not be abused - we advise you to leave about half of the inflorescences on the bush.

By cutting everything, you give the plant a signal to form a large number of new shoots, which will begin to grow everywhere, break the shape of the crown, and also deplete the plant.

Do not break flowering branches: lacerations can lead to plant disease.

Use a sharp garden tool to cut into bouquets. Pruning should be sufficiently long shoots up to two-year-old wood, while leaving no stumps.

It must be understood that when pruning lilacs, we are primarily pursuing the goal of obtaining abundant and strong flowering. Getting enough light, moisture and air, in the crown of a properly formed lilac, each skeletal branch has its own segment for development. Ultimately, pruning forms such a crown through which, as gardeners say, in winter a sparrow can fly without hitting branches with its wings.

How and when to prune a lilac bush? Is it possible to break flowering branches?

Wherever the common lilac does not grow and bloom wonderfully! Beautiful and unpretentious. Own-rooted and grafted. With inflorescences of simple and double flowers of different colors. It would seem that there are no questions related to the agricultural technology of this popular plant. But why then are quite reasonable people convinced that during flowering the branches of a bush are not only possible, but also necessary to break? Where is the confidence that the lilac is not getting worse? Is this true? And why is not yet an old shrub dying, unique varieties are “reborn”, inflorescences are shrinking?

When I pick up a pruner, every time I think over how to carefully correct the shape of an adult bush, prevent thickening, and at the same time not harm the lilac. There is only one alternative: leave the bushes to grow "as they please" and admire the fragrant inflorescences in the garden, and not in a bouquet placed in a vase? But that doesn't suit me.

Let's try to figure out what kind of pruning lilacs need, when to do it, and what tools we need for this.

Pruning in early spring (before flowering)

We have a small lilac alley on the site. So we call that part of the garden where lilac grows along two opposite sides of a wide road. Six bushes of different varieties on each side.

Shrubs have to be pruned several times during the summer. In early spring, I remove (without stumps) all the numerous shoots of overgrowth that appear from all sides and significantly increase the size of the bush. Without such pruning, it will quickly grow and begin to take up much more space than you can afford.

First of all, you need to cut out all the broken, blackened and twisted branches. Take a look at the old ones. Even an inexperienced amateur can recognize them. Often such branches are clumsy and decorated with lichen stains. They only interfere with an adult bush, thicken the central part and bloom poorly. There is no need to feel sorry for last year's frail shoots that grow in the central part of the bush. They lack space, food, and light. Some shoots dried up "on the vine". Others have dry or too thin crowns.

In the spring it is worth removing those shoots that have suffered in the winter-spring period (they are clearly visible). This happens even with frost-resistant varieties. There is no need to spare those thick shoots that have succumbed under the wet snow during the winter thaws.

It is not worth leveling the bush before flowering, as those flower buds that are in the upper part of the shoot will inevitably be removed. It is better to postpone this operation to a later date.

Particular attention should be paid to the grafted lilac and be sure to cut out all the emerging shoots that the rootstock gives. Otherwise, it will quickly grow up and begin to drown out the varietal shoots.

For a long time I have had one white lilac bush shaped like a tree. In the spring, I cut all the growth to keep this interesting shape.

We cut flowering branches during flowering

During flowering, I annually cut branches with the most beautiful inflorescences for bouquets. Along the way, I form a bush: I remove branches that interfere with the passage, shading other plants, etc. I use secateurs (regular and ratchet) or sharp garden shears (for overgrowth). I do not touch young bushes, unless there are special reasons for this.

Do not break flowering lilac bushes. First, ugly injured branches remain. In addition, such a rude attitude towards lilacs often ends badly. Bushes are disfigured, problems with the state of the plant appear (especially in wet weather), branches with peeled bark dry out, etc.

Pruning after flowering

Remove as many dried buds as possible after flowering. Otherwise, the formation of seeds will begin, which will delay the vitality of the plants. Most fruits are tied in varieties with simple flowers collected in inflorescences. Terry, densely doubled and non-fruiting varieties can be cut last.

Inflorescences are cut close to the nearest pair of leaves (or buds) located opposite.

If desired, you can shorten some of the shoots to improve the shape of the bush. All "voids" will be visible only for the first time after cropping.

We form a bush or a tree

I start forming a lilac crown at about three years of age of a seedling. I give him the opportunity to get stronger and get comfortable in a new place. Then I proceed to pruning, allowing you to grow a bush or tree.

Lilac bush . For a bush form, it is enough to leave three to four shoots that will not be directed to the central part of the bush. All crossing and shading branches are cut out. Do not allow the appearance of numerous thickening shoots.

Stamp form . The standard lilac looks very impressive. A flowering tree always attracts attention. But a couple of years ago, I had to abandon the "exclusive" and give the opportunity to grow overgrowth of own-rooted lilacs. Our dog was to blame for everything, which invariably raised its paw near this lilac. We noticed this too late, when the lower part of the trunk began to rot. The lilac had to be planted as a bush in order to preserve the variety.

Lilac standard form is vulnerable. The list of her "enemies" includes trimmers and hoes that cause mechanical damage, sometimes heavy. There is one important requirement: the crown of a lilac tree must be symmetrical. All the kidneys on the trunk are blinded.

Rejuvenate an old lilac bush

An overgrown bush, especially an old one, is a close cluster of numerous branches and shoots.

I process only those sections whose diameter is more than 2 cm. Thick trunks (more than 4 cm in diameter) heal poorly, especially in humid summers. How long the remaining parts will last until the wood rots is a matter of time.

Old bushes have one feature: as they grow up, the lower tier is gradually exposed. At the same time, the quality of flowering deteriorates. Sometimes you have to resort to serious "surgery", up to complete pruning (for own-rooted lilacs). After that, you can expect the growth of new shoots.

It is believed that the grafted lilac is not as durable as the native root. That is why regular pruning is so important to her. Otherwise, you will have to restore, through serious anti-aging pruning, the abundance of flowering lost with age.

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