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Timing for Pruning Flowering Shrubs

Timing for Pruning Flowering Shrubs - Nature Hills Nursery

Nature Hills Nursery |

Every year we get a number of calls about why their particular shrub did not bloom.

So we are here to explain why this might happen, to help you plan ahead to allow your beautiful, abundant flowering shrubs to bloom endlessly.

There are a variety of reasons why a particular plant might not bloom. One reason why your plant might not bloom well is that it received too much shade and not enough sun.

Another reason could be that your plant was given too much lawn fertilizer, which results in beautiful foliage, but a lack of flowers.

But most likely the biggest reason behind your flowering shrubs not blooming is because they were pruned at the wrong time of the year, eliminating the flower buds.

Timing is Key

We are going to select a few shrubs that you need to be aware of so you can keep your plants blooming abundantly in your landscape!

Below is a list of the most common plants that should NOT be pruned until they are done blooming!

Lilac

sensation lilac

The ideal time to prune your Lilac shrubs is as soon as these plants finish blooming. This is the best time because they produce new growth after flowering, so the flower buds bloom on their old wood.

With that being said, if you prune later in the summer, fall, winter, or early spring before they leaf out – you will be removing the flowers that developed in the prior season.

Viburnum

Similar to the Lilacs, these plants can only be pruned after they bloom because the new growth that develops after the bloom period is where the developing blooms for the upcoming year grow.

This is why you might have seen Viburnums have no flowers developing on the top of the shrub, which is where they were pruned, but only flowers on the side branches.

Forsythia

This plant is one of the first to bloom in the spring with elegant yellow flowers throughout its stems!

Let your Forsythia bloom abundantly for weeks and as soon as the flowering is done you can begin to prune. You can even cut it all the way to the ground and allow all new branches to develop fresh flower buds for the next year.

Magnolia

You might see this shrub as low branched, clump formed, or sometimes as single-stemmed, but however they are grown, you must be informed that this plant flowers on last year's wood!

So allow your Magnolia to bloom beautifully, and once it finishes blooming, you can get your shears out and reduce the size or remove dead or damaged branches if that’s what you prefer.

Just keep in mind that the new growth that develops will grow next year’s flowers on them, so leave all the new growth alone for bountiful blooms!

Rhododendron and Azalea

Honey Butter Rhododendron

These spring blooming gems have all of the magic already built into the buds anxiously awaiting for spring right now, so if you went and pruned them now you would be eliminating its flowers.

Let these breathtaking blooms work their magic and once they’re done blooming, you can prune if needed to reduce their size or shape.

If you are growing our popular reblooming varieties then be sure to only trim right after the first set of spring flowers bloom. While there may be some bud production happening on the new growth after, pruning as soon as the first flush of blooms is the best course of action.

Ninebark

Whether you have this plant in shrub form or single-stem tree form, we are here to tell you when to prune this beauty!

You will be blessed with clusters of pink buds opening to white and showy fleshy seeds that all produce on last year’s wood, so wait for them to bloom and after the flowers finish blooming you can trim if needed.

Weigela

Many of the new Weigela varieties will bloom first on last year’s wood and then again later in the season on this year's new growth. In order to get the most flower power, the time to prune is right after the first major flush of flowers in later spring.

Aronia

All of the red and black Chokeberry plants will flower and fruit on last year's wood, so timing is everything!

These plants are usually grown for the delicious fruit, so if you prune in late winter, early spring, or fall before they leaf out and bloom, then you will eliminate flowers and fruit.

In most cases, your Aronia shrub would need renewal pruning by cutting the fattest stems out of the ground and leaving the thinner stems in their place to produce the most flowers.

White snow sensation

Mock Orange

Philadelphus varieties are spring-blooming shrubs, but you’ll want to wait to prune them until after they leaf out and show off their magnificent flowers. After they are finished blooming, you can cut your plant down to your personal preference.

Climbing Roses

In late May and early June, these plants will need their long, older canes to produce an abundant amount of blooms.

Let your plants bloom and when the older canes need to be replaced with younger, thinner canes, you can selectively take out the older, thicker, and damaged canes after the first round of beautiful blooms.

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Frequently Asked Questions

When is the best time to prune spring-blooming shrubs?

The best time to prune spring-blooming shrubs like lilacs, viburnums, forsythia, and magnolias is immediately after they finish flowering. These plants bloom on last year's wood, meaning the flower buds for next season develop on new growth produced after the current bloom period ends. If you prune in summer, fall, winter, or early spring before they leaf out, you will cut off the buds that formed the previous season and sacrifice next year's flowers. Wait for the blooms to fade completely, then get your shears out and prune as soon as possible to give the plant maximum time to set new buds for the following year.

When is the best time to prune summer-blooming shrubs?

The best time to prune summer-blooming shrubs is in late winter or early spring before new growth begins, since these plants set their flower buds on new wood produced during the current growing season. Pruning them while they are dormant encourages vigorous new growth that will carry this season's blooms. Wait until you see the first signs of life emerging from the base of the plant, then cut back as needed to shape or reduce size before the growing season kicks into full gear.

Why does pruning at the wrong time of year cause shrubs to stop blooming?

Many flowering shrubs, including lilacs, viburnums, forsythias, and magnolias, set their flower buds on the previous season's wood, meaning the buds that will bloom next spring are already forming on this year's growth shortly after the current bloom period ends. When you prune in late summer, fall, winter, or early spring, you are cutting off those already-formed buds before they ever get the chance to open. To keep these shrubs blooming reliably, prune them within a few weeks of when they finish flowering, which allows the new growth that follows to develop a full set of buds for the following year.

Can you prune flowering shrubs in the fall without harming next year's blooms?

Pruning most flowering shrubs in the fall will remove the flower buds that developed over the summer, resulting in little to no blooms the following year. Shrubs like lilac, viburnum, forsythia, and magnolia all bloom on old wood, meaning their flower buds form on growth from the previous season. The safest and most reliable rule is to prune these shrubs immediately after they finish blooming in spring, giving them the entire growing season to develop new growth and set next year's flower buds. Hold off on any fall pruning for these varieties and mark your calendar to prune right after bloom time instead.

Can you prune flowering shrubs in winter?

Pruning most flowering shrubs in winter is not recommended, as it removes the flower buds that developed on old wood during the previous season. This is especially true for popular shrubs like lilac, viburnum, forsythia, and magnolia, all of which bloom on last year's growth. The best approach is to wait until each shrub has finished blooming in spring, then prune immediately after to allow new growth to develop next year's flower buds.

How do you know if a flowering shrub blooms on old wood or new wood?

Generally, shrubs that bloom in early spring, such as lilacs, forsythia, viburnum, and magnolia, flower on old wood, meaning they set their buds on the previous season's growth. Shrubs that bloom in mid to late summer typically flower on new wood produced in the current growing season. A simple rule of thumb is that if your shrub blooms before July, assume it flowers on old wood and wait until immediately after blooming to prune. When in doubt, hold off on pruning until you see where the buds are developing, which will tell you exactly what wood to protect.

Should you prune flowering shrubs before or after they bloom?

Flowering shrubs that bloom on old wood, such as lilac, viburnum, forsythia, and magnolia, should always be pruned immediately after they finish blooming, never before. Pruning these shrubs in late summer, fall, winter, or early spring removes the flower buds that developed the previous season, which is the most common reason gardeners find their shrubs failing to bloom. As a general rule, let your shrubs complete their bloom cycle, then get your shears out within a few weeks of flowering finishing to shape, reduce size, or remove dead and damaged branches.

How often should flowering shrubs be pruned to keep them healthy and blooming?

Flowering shrubs like lilac, viburnum, forsythia, and magnolia should be pruned once per year, immediately after they finish blooming. These plants set next year's flower buds on the current season's new growth, so pruning at any other time risks cutting off those developing buds and sacrificing your spring display. Avoid pruning in late summer, fall, winter, or early spring before new growth emerges. Make it a habit to mark your calendar as soon as you see blooms fading, and get your shears out within a few weeks of flowering finishing to keep your shrubs both healthy and floriferous year after year.

When should you prune aronia shrubs?

Aronia shrubs bloom in spring on old wood, so the best time to prune them is immediately after they finish flowering, typically in late spring. Pruning later in the season risks removing the flower buds that have already set for the following year. To keep your aronia healthy and blooming reliably, schedule your pruning within a few weeks of bloom drop and avoid cutting back into the plant during summer, fall, or early spring.

How do you prune overgrown flowering shrubs without losing a season of blooms?

The key to pruning overgrown flowering shrubs without sacrificing blooms is timing your cuts right after the plant finishes flowering. Shrubs like lilac, viburnum, forsythia, and magnolia all bloom on old wood, meaning they set next year's flower buds on the new growth that develops after blooming, so pruning before or during bloom will eliminate that season's flowers entirely. Wait until the last flower fades, then prune as heavily as needed, forsythia can even be cut all the way to the ground to encourage fresh blooming stems. Mark your calendar as soon as you see buds break in spring so you know to hold off on any cutting until the show is completely finished.