When to Prune Flowering Shrubs | Timing Guide

It is important to know when to prune your flowering shrubs, so you get the most flowers. Timing your pruning is the key to success.

Many early spring flowering plants already made their flowers all hidden and tucked away in the growth from last year. Pruning at the wrong time will eliminate those flowers. Here are some tips to keep you in the know.

Let’s take a Lilacs for example…

If you are out in the yard and your Lilac looks large and you have a pruner in your hand, it is late summer - and you just cut off the tips of the branches – your lilac will not bloom in the spring. Let’s say you pruned them in fall, the same thing would happen in spring – no flowers. Let’s say you prune your Lilacs in early spring before they leaf out - same scenario because you are removing the flowers that formed in the growth that developed last year.

There are many different kinds of Lilacs, and the bloom times are common and hyacinthiflora types, then the French Hybrids, then the Miss Kim & Dwarf Korean types, the Canadian hybrids, and lastly…the Japanese tree Lilacs. As each of these kinds of lilacs finish bloom – that is the perfect time to prune each of those lilacs without affecting next years flowers. Older and overgrown Lilacs can be renewal pruned (removing the oldest stems out to the ground) and again right after bloom is done.

Let’s look at some of these other early spring blooming shrubs.

Flowering Quince is an early spring blooming rockstar. Orange flowers bust out early and last for more than a month. Then the plant breeders went to work and introduced many new varieties and new colors and some re-current blooming as well. Trimming Quince varieties is best done immediately after the early spring blooms finish. Then all of the new growth will make next years flower so no pruning after the initial prune is done right after the flowers are done. Those newer varieties can and will throw some additional flowers throughout the summer but keep the pruning to that time following the early bloom always.

Forsythia varieties too have increased in number over the years. Forsythia flowers are a welcoming sunny yellow or gold flowers arranged all along the stems in early spring before the leaves appear.

Forsythia varieties are typically fast growing and are all basically treated the same way for pruning. As soon as the flowers are done (with their sometimes month-long show) in early spring – that is the time to prune! Older and overgrown Forsythia plants can actually be cut down to the ground right after the blooms are done and all new growth will develop and still bloom the following spring. Many of the newest selections remain much smaller and easier to incorporate into smaller landscapes.

Rhododendrons and Azaleas are treated the same when it comes to pruning. Basically, Azaleas are considered Rhododendrons and are all included under the Rhododendron group. Some are evergreen holding their leaves all year, and some do lose their leaves. Reblooming varieties are being introduced all of the time but most of them are hardy in some of the warmer zones.

Pruning Rhododendron and Azalea varieties is sometimes hard for many to want to do – why would anyone want to reduce the size of a plant that flowers on every tip? Well, in some areas they can get big or need a little tweaking to keep them looking like you want them to. Pruning Rhododendron and Azalea varieties can be done right after the first round of flowers begin to fade. A hand pruner selectively reducing the length of any branches back into the body of the plant will allow the plant to continue in its more natural form. Do not be afraid to prune these amazing plants. They will respond beautifully to pruning and still form more flower buds in the new growth that happens after the pruning is complete.

Magnolias are wildly showy and highly valued landscape plants. Some Magnolias are grown as single stem trees, and many more are grown more like large shrubs with low branching or multiple stem plants. Both methods of production are seen across the country, and preference is up to you. Most Magnolias are larger growing plants and are used as a specimen plant or focal point in the landscape.

Pruning Magnolias may be necessary to correct the structure, tweak the form, or reduce the size a bit. Pruning should only be done right after the amazing flowers finish. (kind of a theme here).

Weigela plants have had extensive interest with breeders also. New selections offer new form, smaller size, great and varied leaf color & flower colors, and reblooming capabilities stronger than ever. Flowers in spring are best on last years stems so do not trim Weigela until that first round of flowers are done blasting off in June in many areas. Waiting will allow your plants to bloom as heavily as Azaleas do, covering the stems with trumpet shaped flowers that the hummingbirds love.

Older Weigela varieties were much larger and most likely need more pruning then the newer, smaller selections. Larger, older selections can be renewal pruned by removing the oldest stems out to the ground leaving the thinner and smaller stems to take over. If very overgrown you can wait until the first round of flowers finish and cut the branches all down to the ground and allow new shoots to take over and bloom on the tips in fall and the following spring too.

Birch and Maple trees can bleed sap if pruned early spring, so if you wait until they have leafed out, those cuts will not bleed and heal over quickly.

Spring Flowering Bulbs are so very welcome in the landscape. Keep your bulbs happy and healthy by pruning them the right way. Enjoy the flowers. When the flowers finish, remove only any seed heads that might form leaving all other green parts of the plants remain. These green leaves and flower stems make food for the bulbs and will keep your flowers next year larger and healthy. Many people like to cut off the leaves when the flowers are done but wait to cut any of the leaves off until they turn yellow and they have done their job of making more food for the bulbs.

We hope this help you get the most flowers out of your shrubs! If you have specific pruning questions, you can send them to info@naturehills.com, and we would be pleased to help you.

Frequently Asked Questions

When is the best time to prune flowering shrubs?

The best time to prune flowering shrubs depends on when they bloom. Early spring bloomers like lilacs, forsythia, and flowering quince set their flower buds on the previous year's growth, so pruning them in fall, winter, or early spring will eliminate that season's blooms. The golden rule is to prune these shrubs immediately after their flowers fade in spring, which gives the plant the rest of the growing season to develop next year's flower buds. Always time your pruning to the bloom cycle of each specific shrub rather than following a one-size-fits-all seasonal schedule.

How do you prune flowering shrubs without losing blooms?

The key to pruning flowering shrubs without sacrificing blooms is understanding whether your plant blooms on old wood or new wood. Early spring bloomers like lilacs, forsythia, and flowering quince form their flower buds on the previous year's growth, so pruning them in late summer, fall, or early spring will remove those buds before they ever open. The golden rule for these shrubs is to prune immediately after their flowers fade, giving the plant the rest of the growing season to set next year's buds. Follow this simple timing rule and you will enjoy full, abundant blooms year after year.

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

Many flowering shrubs, including lilacs, forsythia, and flowering quince, set their flower buds in the previous season's growth, meaning the blooms for next spring are already tucked inside the branches by late summer or fall. If you prune during late summer, fall, or early spring before bloom, you are cutting off those already-formed buds and eliminating the flower display for that year. The simple rule to follow is to prune spring-blooming shrubs immediately after their flowers fade, which allows the plant to spend the rest of the growing season producing new growth that will carry next year's blooms.

When should you prune yellow bells shrubs?

Yellow bells, also known as Forsythia, should be pruned immediately after their flowers finish in early spring, which typically wraps up after a show that can last nearly a month. Pruning at any other time, whether in summer, fall, or before spring bloom, risks cutting off the flower buds that formed on the previous year's growth. For overgrown or older plants, this post-bloom window is also the right time for more aggressive renewal pruning. Make it a habit to get out there with your pruners as soon as those last golden flowers fade.

When is the best time to trim lilac bushes?

The best time to trim lilac bushes is immediately after they finish blooming in spring. Pruning at any other time, whether in late summer, fall, or early spring before bloom, removes the flower buds that formed on the previous year's growth and will result in no flowers the following season. Different lilac types bloom in sequence, so follow each variety's specific bloom period and prune right when the flowers fade. For overgrown or older lilacs, use renewal pruning by removing the oldest stems down to the ground, again timing this right after bloom is complete.

How do you properly prune a lilac bush to keep it healthy?

Prune your lilac bush immediately after it finishes blooming in spring, as lilacs set next year's flower buds in the new growth that develops right after bloom. Pruning at any other time, whether in late summer, fall, or early spring before leafing out, will remove those hidden flower buds and result in no blooms the following year. For older or overgrown lilacs, use renewal pruning by removing the oldest and largest stems down to the ground, again timing this right after the blooms fade. Follow this simple rule: flowers done, pruners out.

Should you prune spring flowering shrubs before or after they bloom?

Spring flowering shrubs like lilacs, forsythia, and flowering quince set their flower buds on the previous year's growth, so pruning before bloom will remove those buds and eliminate your flower display. Always wait until immediately after the blooms fade to prune these plants. This timing allows the shrubs to produce new growth throughout the remaining season, which will carry next year's flowers. Make your cuts right as the last petals drop to get the cleanest results without sacrificing next spring's show.

Can you prune flowering shrubs in summer without harming next season's blooms?

Pruning most flowering shrubs in summer will cost you next season's blooms, because early spring bloomers like lilacs, forsythia, and flowering quince set their flower buds in the previous year's growth. If you cut into those stems in late summer or fall, you are removing the very buds that would have opened the following spring. The safe window for pruning these shrubs is immediately after they finish flowering in spring, which allows the plant to set new buds on fresh growth throughout the rest of the season. To protect next year's display, put the pruners away once summer arrives and mark your calendar to prune right after bloom time instead.

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

Shrubs that bloom in early spring, like lilacs, forsythia, and flowering quince, almost always bloom on old wood, meaning they set their flower buds on the previous season's growth during summer and fall. Shrubs that bloom in mid to late summer, like butterfly bush or rose of Sharon, typically bloom on new wood that they produce in the current growing season. A simple rule of thumb: if it blooms before June, assume old wood and prune right after flowering finishes; if it blooms after June, prune in late winter or early spring before new growth begins.

Can you cut back overgrown flowering shrubs hard without killing them?

Yes, most overgrown flowering shrubs like Lilacs and Forsythia can handle hard renewal pruning without being killed. The key is timing your cuts correctly, which means waiting until immediately after the shrub finishes blooming to avoid sacrificing next season's flowers. For the hardest cases, use a renewal pruning approach by removing the oldest, thickest stems all the way down to the ground. Work in stages over two to three seasons if the shrub is severely overgrown, which reduces stress on the plant and keeps some flowers coming each year.