10 Shrubs You Should Prune This Spring and 5 You Should Never Touch

Spring has come, with lots of flowers, sunny days, mild climates and… Lots of work for gardeners! Look at your shrubs for example; do they look healthy? Or are they overgrown, maybe sickly, and in need of help? Then it’s time to feed them, true, but also prune them. But not all of them! Some varieties need a good and healthy trim in this season, while others don’t – as you would damage them and their blossoms?

But which is which? And – above all – how can you prune your shrubs in spring professionally? You are about to find out, but first of all…

Basic Pruning Rules – To Do It Like a Professional

Pruning is the “surgery of gardening”, and in fact, we talk about “tree surgeons”. It’s true that many shrubs are much more forgiving than trees, but you still need to be careful, and follow some basic rules.

• Always use tools with sharp blades.
• Disinfect the blades before and after each shrub, or you risk spreading diseases around your garden.
• Cut branches above a stem or gem at 45° angle with the tip on the side of the stem or gem; this will allow water to slide off easily, so it doesn’t stop and it doesn’t penetrate into the branch.
• Always remove all cut branches after you have pruned your shrubs; if you leave them there, they can rot, become breeding ground for fungi and bacteria, and spread diseases.
• Whenever possible, try to follow the natural shape of the shrub.

And now, some jargon of the trade…

The 3 D’s of Pruning

Professional gardeners call them “the 3D’s”, and they mean “dead, diseased and damaged branches”. Always start your shrub pruning by removing these. It will give you a clearer picture of what to cut next.

Moreover, we will see some shrubs that you mustn’t prune in spring, but the 3D’s are an exception; you can always cut dead, diseased and damaged branches.

Finally, keep in mind that by “diseased” we mean visibly, so; don’t cut a branch for a little spot or some minor ailment you can cure if it is healthy overall. Similarly, by “damaged”, we mean heavily and beyond repair.

But what tools do you need?

The Tools You Need to Prune Shrubs

You will need some basic tools and know how to use them to prune your shrubs:

• Bypass pruners; these have two blades, and they are good to cut small and green stems.
• Anvil pruners; they have one blade and a flat surface and they are used to cut dead and dry branches. Do not use them for green ones, or you will damage them!
• These two are both called “hand pruners” and you should use them for stems, canes and branches that are up to 2/3 inch thick (2.0 cm).
• Loppers; you will use these for branches that are more than 2/3 inches thick (2.0 cm).
• Pruning saws; they can be folding, bow or curved, and you will use them for woody and thick branches, from 2 inches thick (5.0 cm) onwards.

To use pruning saws, you need three cuts:

–          The undercut; saw a notch about 6 inches from where you want the final cut (15 cm).

–          The top cut; saw where you have the notch.

–          The Final cut; finally saw above the collar of the branch, that swollen part at its base.

This way, your cuts will be neat and healthy.

But which shrubs should you be pruning in spring? And how? Off we go!

1. Dogwood (Cornus spp.)

We keep bare dogwood branches in winter because they look wonderful. These shrubs can keep our gardens colorful during the cold season. But, as spring comes, they need pruning, or they won’t look good and healthy. Try to cut them early in the season, and there are three methods; here they are:

• In all cases, cut dead, diseased or damaged stems first.
• For what’s called the “annual pruning”, select the strong stems, and thin out the shrub by cutting smaller and weaker branches at the very base of the shrub.
• If your dogwood is overgrown, it will need what’s called “hard pruning”; in this case, cut all the stems to 6 inches (15 cm) above ground level.
• Every 2 to 3 years, dogwood shrubs will also need “rejuvenating pruning”. In this case, cut 1/3 of the older stems down to ground level.

That’s all!

2. Barberry (Berberis thunbergii)

So, have you enjoyed the glossy red berries of barberry through the winter season? It’s time to prune it then, now that it is early spring! Don’t delay though, as it will soon be flowering. And, again, you have different methods, according to your and your shrub’s needs.

• Always cut dead, diseased and damaged stems first, after winter there can be a few.
• Also cut smaller and weaker stems.
• Always cut before upward and outward facing gems or stems.
• For heavy pruning, cut about 1/3 of the older stems.
• If instead you want to keep it in size, prune all the stems 6 to 12 inches (15 to 30 cm) from the ground, which will also rejuvenate your barberry shrub.

3. Summer-Flowering Viburnum (Viburnum plicatum, Viburnum dentatum)

If your viburnum shrub flowers in summer, early spring is a good time to prune it, so it can grow new stems and give you lots of those round, white clusters of flowers we all love! However, you need to do it early in the season, in March, or you actually risk ruining its floral display. Here’s how to go about it:

• Cut all dead, diseased and damaged wood.
• If it is overcrowded, prune 1 or two of the older stems, cutting them down at ground level.
• Cut crossing stems, to improve ventilation and avoid competition.
• To keep it in size and shape, instead, cut back overgrown branches, before an outward and upward pointing bud.
• To rejuvenate the shrub (every 2 to 3 years), cut 1/3 of the oldest stems to ground level.

We will see which varieties of viburnum you mustn’t prune in spring later on in this article.

4. Crape Myrtle (Lagerstroemia indica)

Crape myrtle will start blooming in early summer, so you can give it enough time to produce the flower buds if you prune it in early spring. What’s more, whether you keep it as a shrub or as a tree, it blooms on new wood, so, a good cut will encourage new growth, and it will literally fill with its super bright, showy deep pink blossoms if you do!

• Cut all dead, diseased and dying wood.
• Also cut weak branches.
• Cut all suckers; they won’t bloom.
• Cut crossing stems.
• Trim back spent flower clusters or sets of pods, if you still have them.

However…

• Never top branches (cut the last part), this is called “crape murder” in the gardening jargon, and never cut interior branches.

5. Summersweet (Clethra alnifolia)

As its name suggests, summersweet wil grace your garden with its long, plume-like clusters of small white flowers in July and August. However, you should prune it in early spring, to give it time to grow new stems that bear all those lovely flowers. Once again, there are different types of pruning for this shrub.

• In all cases, prune all dead, diseased, damaged and also weak branches.
• Cut crossing and rubbing branches.
• Cut 1/3 of the height of the shrub, to keep it in shape.
• To rejuvenate it (every 2 to 3 years) cut the oldest, woody stems to ground level and…
• Cut the others 6 to 12 inches (15 to 30 cm) above ground level.

It’s quite simple in the end.

6. Butterfly Bush (Buddleja davidii)

Butterfly bush is yet another shrub that flowers on new wood, so, cutting back the old stems in early spring promotes new growth and lots of those purple, conical clusters of little flowers that attract so many pollinators in your garden. It also helps you keep it in size and shape, so, when it blooms from mid summer onwards, you will have a compact but floriferous mound of leaves and blossoms.

• As usual, cut all dead, diseased and damaged wood first.
• Cut back all stems to 12 to 24 inches above ground (30 to 60 cm), to keep butterfly bush compact.
• Give it a round shape.
• If you still have spent blooms on, deadhead them.

While pruning butterfly bush shrubs is very easy, avoid over-pruning, and they will be fine.

7. Elderberry (Sambucus canadensis)

You can prune elderberry after it fruits in fall, but if you haven’t done it yet, you must definitely act soon, in early spring. In fact, this very vigorous shrub needs a “heavy cut” at the beginning of this season, to promote new growth, but also to keep it in size, or, come summertime, you will have a massively overgrown bush in your garden.

• Cut all dead, diseased and damaged wood; blackened and whitened stems are typical with elderberries in early spring – cut them as they are sick.
• Cut 1/3 to ½ of all old wood! It’s a lot…
• Thin out the shrub; keeping distanced branches and cutting all weak ones.
• After all this, you still need to cut 1/3 of all remaining growth to keep it in size.
• Try to cut for ventilation and space; each branch will grow a lot of new stems and leaves.

I suppose elderberry is the shrub that needs the heaviest pruning of all, unlike my next choice…

8. Weigela (Weigela florida)

Unlike elderberry, weigelia only needs light pruning, unless you want to rejuvenate it (every two to three years). On the other hand, you have two short slots to do it in this season: early spring, before it blooms or late spring to early summer after it has blossomed. “Hold on,” you may say, “but this shrub flowers in spring!” And you are right, but it does so on old wood, so you won’t stop it growing and opening buds if you give it a light trim.

On the other hand, if you regenerate it, it won’t bloom as much that year, but a lot the next.

• First of all, cut all dead, diseased and damaged wood.
• Then, prune weak and straggling branches.
• Also cut back overgrown branches, to keep it in size.
• To rejuvenate it, cut all the branches and stems down to 12 inches from ground level (30 cm).
• Easy, isn’t it?

9. Potentilla (Potentilla fruticosa)

Potentilla is a small shrub indeed, growing to a maximum of about 4 feet (120 cm) and 5 feet wide (150 cm), but it can get very dense, and this may hamper its flowering ability when it blooms, which is soon, from late spring to early summer. So, if you want to enjoy that big display of golden in white, golden yellow, pink or red, you must act quickly and prune it early in the season, in March. And here is how to do it in three ways:

• Cut all dead, diseased and damaged branches for each type of pruning first.
• For annual light pruning, you should cut weak, crossing and leggy branches back to the base, then…
• Prune about 1/3 of the height of the shrub.
• To thin it for ventilation, cut 1/3 of the oldest and hardest branches back to the base. You should do this every 2 to 3 years.

·         Finally, to rejuvenate potentilla, cut the whole shrub back to 12 (30 cm) inches above ground level. Do this every 3 to 5 years.

And finally…

10. Lilac (Syringa vulgaris)

We finish with one of the most beautiful, generous and popular flowering shrubs ever: lilac! You need to be very careful with it, because there are two distinct types of pruning, and they must be done at different times!

Light pruning must be done in late spring or early summer, after it your lilac shrub has bloomed, while rejuvenating pruning in late winter or early spring, and that year, you won’t get flowers, and maybe the year after too.  And here is how to do both.

• In both cases, always cut dead, diseased and damaged wood, then…
• For annual light late spring and early summer pruning:
• Cut weak and small branches back to the base.
• Cut all suckers.
• Cut 1/3 at the top of the shrub to control your lilac’s height.
• For rejuvenating pruning, in late winter or early spring, every 10 to 15 years:
• Cut the whole lilac shrub back to 6 to 12 inches above ground level (15 to 30 cm).
• This is usually done for old and neglected lilac shrubs, however, there is a “middle way”, which is a “light rejuvenation” pruning, to do in late winter or early spring:
• Cut 1/3 of the oldest, less productive stems, especially very tall ones, down to ground level and leave the others. This can be done every 2 to 3 years and you will still get blossoms from the other branches.

These are the shrubs you can prune in spring, but which are the varieties that you mustn’t?

Shrubs You Mustn’t Prune in Spring

There are some shrubs that you mustn’t prune in spring, and these are usually varieties that bloom before June. With these, you will usually have to wait till after they have flowered. However, remember that you can always cut the 3D’s, dead, diseased and damaged wood: this is a health treatment for your shrubs, and after long and harsh winters, they may need it.

Let’s meet 5 of them and see why.

1. Spring-Flowering Viburnums (e.g., Viburnum carlesii, Viburnum opulus)

If you are growing spring flowering varieties of viburnum you cannot prune them in spring, and the reason is very simple, unlike summer blooming ones, they will grow and open their blossoms on old wood. So, if you cut them, you simply won’t get them!

2. Witch Hazel (Hamamelis spp.)

Witch hazel is a very popular and easy to grow, low maintenance shrub. But the biggest mistake you can make with it is to prune it in spring! The reason is that it takes ages to grow its flower buds. In fact, it starts in late fall and early spring, and if you cut it now, you will also eliminate all the blooms…

3. Rhododendron & Azalea (Rhododendron spp.)

Rhododendrons and azaleas must be some of the most beautiful flowering shrubs in the world! But, in order to give you those breathtaking floral displays, they work for months and months on end. They will start producing new buds as early as late summer or early fall.

So, again, if you prune rhododendrons and azaleas now, you will also cut all the flower buds – and you don’t want that…

4. Forsythia (Forsythia spp.)

Forsythia is a real marvel of nature; its blooming season can turn your spring garden into a sea of golden yellow. And that’s the point… It flowers far too early to prune in spring… Actually, it will start producing new buds about two weeks after its amazing floral spectacle. So, you may have to cut it in spring, but after it has blossomed.

5. Bigleaf and Oakleaf Hydrangea (Hydrangea macrophylla, Hydrangea quercifolia)

Finally, never prune bigleaf and oakleaf hydrangea varieties in spring, because they flower on old wood, and if you do, you will be cutting the buds as well. Wait till they have blossomed before you take your loppers out!

To Prune or Not to Prune – That Is the Question in Spring for Shrubs Finally, I will leave you with a general rule of thumb, in case you have shrub varieties that are not on this list: if it blooms before June, do not prune it, and wait till it has flowered.