Pruning of shrubs

Some shrubs need pruning but why, when and how to prune?

Why prune ?

Pruning allows you to put your shrubs back in shape and to limit the space occupied by them. In small gardens, it is sometimes necessary to be able to control the expansion of its plantations.

Pruning increases the branching of shrubs by causing new branches to appear under the cut and often improves flowering.

When should we prune?

Shrubs should be pruned at the end of winter, in February or March after heavy frosts, except for winter or spring flowering shrubs for which we will wait until the end of flowering. It would be a shame not to take advantage of them, especially since they have been chosen for their flowers.

For example, for spring or winter flowering shrubs, we can mention the laurel, the forsythia, the flowering currant, the Japanese quince, the Japanese cortea, the spring spirea...

Other shrubs do not need pruning or even would not tolerate it like the rhododendron, the azalea, the magnolia, the camellia or the skimmia. You can however remove the faded flowers.

How to prune?

For maintenance pruning, we distinguish evergreen shrubs from deciduous shrubs.

For deciduous shrubs such as hydrangea, lilac or seringat :

• Remove dead or diseased branches and frost-burned branches.
• Cut back unsightly branches
• Cut off wilted flowers to prevent unnecessary fruit production
• Cut the oldest branches at 5 cm from the ground to aerate your shrub and allow light to penetrate inside
• Do a rejuvenation pruning

You can do a rejuvenation pruning every 3 or 4 years by cutting them back severely.

For evergreen shrubs such as laurel, cedar or yew:

• Remove dead or diseased branches and frost-burned branches.
• Cut back unsightly branches
• Prune for shape

Pruning summer flowering shrubs

Summer flowering shrubs illuminate the garden with their bright colors throughout the summer and sometimes until the first frost. To take full advantage of their beauty, a few pruning steps must be taken.

The right time to prune

The majority of summer flowering shrubs have the particularity of flowering on the year's branches. Pruning at the end of winter will be beneficial because it encourages branching and the emission of new shoots that will then flower abundantly in summer. To make this possible, pruning should not be too late as it would compromise or delay flowering. The best time to prune these shrubs is in February or March, outside of the frost period, before vegetation starts to grow again on deciduous species.

How to prune summer flowering shrubs?

Protect yourself with gloves and use pruning shears and a lopper if the shrubs have branches with a larger diameter.

Training pruning

On young and newly planted shrubs, a so-called "training" pruning may be necessary. It stimulates the growth of the plant while giving it a harmonious shape. It consists in reducing the stems by half by pruning above an outward facing eye or to put in place the carpenter branches. Indeed, keeping a low framework on certain shrubs will allow to make a maintenance pruning much lighter in order to keep the volume of the plant. A common trunk will then carry 5 to 6 carpenters which will each divide into 2 or 3 branches. Young baguenaudier, deciduous ceanothus, Hydrangea paniculata or arborescens, Spanish broom or summer tamarisk are concerned by this pruning.

Maintenance pruning

This is the most frequent pruning which allows to stimulate the departure of new flower-bearing shoots. It consists of removing all dead, diseased or damaged branches at the base of the shrub and also clearing the center of the shrub in order to bring in a maximum of light. The shrub is then aerated, the light rays penetrate in its center and a good air circulation is maintained. Pests and diseases will be less frequent on a pruned shrub.

To finish your maintenance pruning, cut the ends of the branches for a few centimeters always above a bud turned towards the outside, in order to give an aesthetic shape to the shrub and to stimulate the growth of new shoots which will bloom as soon as the summer. At the same time, cut off the branches that flowered the previous year. This pruning can be done on most summer flowering shrubs such as Buddleia, ceanothea, hibiscus, perovskia, summer spirea, caryopteris, lavatera or altheas.

Rejuvenation pruning

This is done on aging shrubs that bloom less and less or on very weak subjects that are still growing despite optimal care.

This pruning consists in cutting the stems at 20 or 30 cm from the ground. Caryopteris, rustic fuschia, Leycesteria, Lespedeza, shrub sage, but also Perovskia can be pruned this way.

Pruning hydrangea flowers

The florist's hydrangea produces towering white, blue, purple or pink pompons depending on the variety and soil type. The timing of flower pruning has often been a subject of discussion among gardeners. Some choose to prune them after flowering, others insist on keeping them until the following spring. Who is right?

Pruning time, the big question...

The Hydrangea genus is divided into several species that can be found in the garden, including the famous Hydrangea macrophylla, better known as the florists' hydrangea. Cultivated in pots on a terrace or a balcony, it is also planted in the garden in a half-shaded place where it brings its note of romanticism thanks to its big pompons from July to October. The hydrangea appreciates soils with a rather acidic tendency, its flowers can moreover change color passing strangely from bright blue to pink in too calcareous soil.

The pruning of hydrangea flowers is generally done in spring after the last big cold in regions with a harsh climate, that is to say in March-April before the vegetation wakes up. Be careful, however, because this hydrangea blooms on the previous year's stems. If the pruning is too drastic, you risk not taking advantage of its beautiful summer bloom! It is therefore not advisable to prune all the stems, but rather to opt for a selection that will ensure the renewal of the shoots without sacrificing the flowers. In regions where snow and frost are not uncommon, faded flowers protect buds and young shoots from the cold. Another advantage: they cover themselves with frost, bringing a fairy note to the garden!

In the mildest regions, pruning can be done just at the end of the flowering period, so that the flowering branches have more time to form.

How to prune hydrangea flowers?

1. In regions with mild winters, proceed at the end of the blooming period by pruning the end of the flowering stems at a bevel just above a pair of buds. You can prune up to 25 cm of stem to give a harmonious ball shape to your shrub. If the subject is very old and less floriferous from year to year, cut the oldest branches at their base just above an eye if possible directed towards the outside.
2. In regions with harsh winters, cut off spent flowers by pruning just above the first bud below the flower when there is no risk of frost in spring. Don't prune too low or your hydrangea may not bloom that year!

In both cases, take the opportunity to remove dead or damaged branches and weak stems that are entangled in the center of the shrub in order to aerate it. This operation limits the installation of parasites which particularly appreciate the plant clutter.

Don't forget to sprinkle a mixture of compost and ground horn powder at the foot of your hydrangea after pruning, to help restart the vegetation.

Pruning small shrubs

Small shrubs generally require little pruning, but it is still useful to keep the plant in a harmonious shape and to prevent it from becoming bald. The removal of wilted flowers, dead or diseased branches will also be part of the program, your shrubs will be better off!

The different pruning methods used on small shrubs

The removal of dead wood or diseased branches can be done all year round, it can be completed by the removal of wilted flowers just after flowering. It consists of systematically cutting these parts down to the level of a healthy and full of life branch. Always cut above an eye or an outward facing shoot. This pruning can be done on the majority of shrubs and concerns in particular the lavenders which can be pruned in the shape of balls.

The removal of the old wood allows to aerate the plant while privileging the more recent branches which will thus receive an influx of sap and light and will be able to develop better. It is practiced at the beginning of spring towards the end of March and consists in cutting down between 3 and 5 cm from the ground the 3 years old branches which already carry lateral and sub-lateral branches. This operation concerns Berberis, cotoneaster, brooms, hydrangeas, shrubby veronicas and symphorines.

The limitation of the development is necessary on certain plants, in particular the climbing shrubs or with untidy port, which need to be contained not to invade all and to preserve a compact and pleasant port. These plants should be pruned just after flowering so as not to compromise the next year's flowering. It will be necessary to reduce the branches to the desired height, then remove the oldest stems to keep only the young clumps starting from the ground or from quite low on the old stems. This pruning is done on clematis, climbing hydrangeas, honeysuckles and Turkestan knotweed.

Cutting back is a drastic method that will only be practiced after several years on evergreen shrubs, when they start to recede from the base. This pruning will be done in spring on late flowering shrubs and in autumn on spring flowering shrubs. It consists in cutting all the aerial parts of the plant at about 15 cm from its base to keep only some main branches. A compost-based mulching will then be necessary as well as a contribution of fertilizer in order to ensure the recovery. The following are concerned: St. John's wort, dogwood which will provide beautiful colored stems, Leycesteria, Japanese spirea and santolin.

Small shrubs that bloom on the previous year's wood, such as Buddleia, deutzia, mahonia or weigelia will be pruned immediately after flowering. Pruning will help to maintain a harmonious shape and to obtain larger flowers but in lesser numbers. Stems that have flowered should be cut back just above an eye or new growth, taking care to keep a portion of the current year's branch.

Shrubs that bloom on the current year's stems, such as Buddleia davidii, caryopsis or fuchsia, can be pruned shorter as soon as new leaves appear. Prune all the previous year's stems at 3 eyes from their junction with the old wood that should always be kept.

Pruning the oleander

The oleander can be led in hedges, isolated subject or even in tree. In the coolest regions, it will be grown in pots under cover. Whatever its use, adequate pruning will be required to get the best out of this fantastic plant.

General information about pruning the oleander

The oleander is a beautiful, naturally bushy shrub that grows beautifully when cultivated in an optimal way. For this, it needs heat, sun and water. Once these parameters are required, it will be appropriate to prune it, knowing that this type of shrub only flowers on the most recent branches. A too drastic pruning will therefore logically compromise the next flowering.

Pruning should only be done on subjects older than 5 years, and only every other year or even every third year, except in the case of the formation of a shrub on a stem which will require the removal of shoots and lateral branches every year.

The different types of pruning

Depending on its use, the laurel can be pruned in various ways but always respecting the principle that this operation must be carried out with care and at the right time.

Stem pruning

A beautiful oleander pruned into a stem will later become a very ornamental flowering tree. To achieve this, it is necessary to prune all the peripheral branches as well as the lateral branches every year in order to keep only the main stem which will grow to become a powerful trunk. This technique is ideal in the gardens of the South of France where the subject will have all the necessary conditions to develop well.

Pruning the bushy oleander

As we have seen, the laurel tends to grow very freely in the form of a spreading bush. The goal will be both to clear the center of the shrub and to reduce its spread. The best time is after flowering in the warmer regions, or in April everywhere else.

Proceed on a subject at least 5 years old. Using the lopper, prune all dead branches at the base. Remove also in the center of the clump the branches which cross in order to let penetrate the light and the air to the maximum in the plant and thus to avoid the installation of parasites. Then cut the end of the oldest stems on 1/3 just above a pair of leaves.

Try to keep a maximum of branches from the previous year to be assured of a beautiful bloom. It is generally recommended to prune only 1/3 of the existing stems per year. Rotate the pruning in the following years in order to keep the shrub in good shape while ensuring future flowering.

Pruning oleanders in hedges

A common mistake is to prune oleanders drastically each year to obtain a straight hedge. However, all the interest of this type of hedge lies in its wild and flowery side during nearly 6 months. The same advice as for the pruning of the bushy laurel will therefore be applied to the hedges so that they are both full and offer an opulent bloom.

Pruning oleander in a container

The purpose of this pruning is to maintain a compact subject in order to winter it easily indoors. Prune in autumn, just after flowering. Remove the dead branches or those that cross and reduce the plant in width and height, but always keeping if possible the branches of the previous year on which the flowers will be formed.

The size of the lilac

The lilac is a shrub that gives off sublime fragrances in spring. However, its pruning is subject to controversy, with some gardeners insisting that it should be pruned only rarely and very lightly, while others do not hesitate to prune it back. Wouldn't the middle way be the best solution?

When to prune lilac?

The lilac can be pruned in two stages: in spring just after flowering to remove the faded flower clusters, then in autumn or winter for maintenance and cleaning. Note that this type of pruning will not be done on a young subject that is still too sparse. Wait at least 4 years after planting to consider a thinning out or a 'transparent' pruning.

Be careful, the lilac blooms on the previous year's shoots, if you prune too short and without restriction late in the fall or winter, you risk not enjoying its flowers the following spring!

How to prune lilac after flowering?

Use pruning shears whose blades have been disinfected beforehand (methylated spirits, flame...) and sharpened to ensure a clean and straight cut.

Just after flowering, cut back the deflowered stems by cutting just above the first big bud present under the flowering stem. Cut neatly, beveling away from the bud so that rainwater does not run directly onto it but on the other side. The bud will have time to develop and form a flowering stem for the following spring.

How do I do a cleaning pruning on the lilac?

As we have seen above, this pruning should only be considered on an old subject whose structure needs to be aerated.

Take a pruning shears whose blades will have been disinfected and well sharpened beforehand.

• In the fall or winter, cut back ¼ of the oldest stems at the base of the plant. This operation will encourage the birth of new stems while preserving enough branches to obtain a beautiful bloom.
• Take the opportunity to remove all the dead wood and branches that cross in the center of the shrub. The silhouette will thus be aerated and the shrub will be less prone to harboring pests. Better ventilated, the lilac will also be less likely to suffer from diseases.
• Cut off any suckers at their base.

How to prune lilacs back?

Rejuvenation pruning can be considered for very old trees that are not flowering well and have a gangly habit. This pruning is done at the end of winter in March or even a little earlier in the mildest regions, just before budburst.

• Take a pruning shears or a hand saw. Do not forget to sharpen and disinfect the blades beforehand.
• Remove all dead branches at their base and 1/3 of the oldest branches.
• Cut back the other branches to 30 cm from the ground by pruning just above a bulge in the bark (bud) facing outwards.