How to prune shrubs without harming them?

When to prune shrubs for optimal growth?

For summer-flowering shrubs (flowering on new wood), prune in late winter or very early spring, before the end of April, to encourage abundant flowering.

For spring-flowering shrubs (flowering on previous year’s wood), wait until after flowering to prune them, unless you’re prepared to sacrifice this year’s blooms.

Rejuvenation Pruning: How to Revitalise an Ageing Shrub?

Hard pruning is a radical yet highly effective method to rejuvenate an ageing shrub or one that’s becoming bare at the base. It involves cutting the main branches down to 5-15 cm above ground level to stimulate new shoots from the stump. The weakest or dead branches should be removed by cutting them flush with the ground, leaving only the most vigorous stems.

Which shrubs can be hard pruned?

Some shrubs respond very well to hard pruning, promoting vigorous regrowth. Flowering currant (Ribes sanguineum), Hydrangea ‘Annabelle’ (Hydrangea arborescens), Japanese kerria (Kerria japonica), spirea, and tree mallow quickly produce new flowering shoots. Russian sage, St John’s wort, forsythia, mahonia, mock orange (Philadelphus spp.), weigela (Weigela florida), rose of Sharon (Hibiscus syriacus), and Himalayan honeysuckle (Leycesteria formosa) also tolerate hard pruning well, which stimulates their growth and flowering.

Conversely, other shrubs cannot withstand hard pruning, as they do not readily regenerate new shoots from old wood. This is the case for Japanese maple, abelia, daphne, and witch hazel, which prefer light pruning to maintain their structure. Contorted hazel (Corylus avellana ‘Contorta’) loses its charm if pruned too severely, while decorative viburnums like Viburnum plicatum, Viburnum carlesii, or Viburnum calcephalum may not flower properly after drastic pruning.

How to do it?

Make a clean, angled cut about 5 mm above an outward-facing bud. This slope prevents rainwater from pooling on the cut, reducing the risk of disease.

Be mindful of the cutting height:

• If you cut too close to the bud, you risk damaging it.
• If you leave too long a “stub,” it will dry out unnecessarily and may become a breeding ground for disease.

A special case: lavender

Never cut an old lavender branch if you don’t see buds or young shoots near the base (otherwise, no regrowth will occur). Only a few varieties readily produce such buds and can therefore be rejuvenated regularly. These include ‘Hidcote Blue’. Other varieties age poorly and should be replaced every three to five years.

Thinning Size: Why and How to Prune Your Shrubs?

It is often said that “a swallow should be able to fly through the shrub,” a vivid expression from the past that perfectly illustrates the goal of thinning pruning: allowing light and air to circulate freely through the branches. This technique aims to open up the shrub’s structure, thereby promoting better plant health by reducing the risk of fungal diseases and encouraging balanced growth.

Which Shrubs Should Be Thinned?

Thinning pruning is particularly suitable for shrubs with decorative flowering and dense foliage. These include ornamental cherry trees (such as Prunus serrulata), laburnum (Laburnum), and broom (Cytisus), whose branches tend to intertwine easily. The dogwood (Cornus), prized for its colourful winter stems, benefits from regular thinning to maintain vibrant young shoots. Weigela, lilac (Syringa vulgaris), as well as azaleas and rhododendrons, gain vigour after this pruning, leading to more abundant flowering. Photinia, valued for its bright red spring foliage, and Japanese quince (Chaenomeles japonica), with its striking blooms, also thrive with thinning pruning for better development.

How to Proceed?

Thinning involves removing entire branches by cutting them at their point of attachment to a main branch or directly at the base of the shrub. The goal is to target:

• Older branches, recognisable by their dull, cracked bark, often less productive in flowers or foliage.
• Poorly oriented branches, which cross or rub against others, creating weak points.
• Excessively thin shoots, weak or lacking vigour, which do not contribute to the overall structure.
• Dead or broken branches, which act as entry points for disease.

Make clean, precise cuts, as close as possible to the attachment point, without leaving stubs. These leftover bits of wood tend to rot, becoming potential breeding grounds for fungi and other pathogens.

Mistakes to avoid when pruning shrubs

• Prune at the right time according to flowering.
• Respect each shrub’s specific needs.
• Use clean and sharp tools.
• Make clean and precise cuts without stubs.
• Thin out the shrub by removing dead or poorly positioned branches.

To go further: our tips for successful pruning

To deepen your knowledge about pruning shrubs and avoid damaging them, I invite you to read the following articles on our website:

1. Pruning fruit trees, shrubs and roses: 10 mistakes to avoid
   This article details common mistakes to avoid when pruning to preserve your plants’ health.

2. How to prune and maintain evergreen shrubs?
   Discover tips for properly pruning your evergreen shrubs and maintaining their beauty throughout the year.

3. Pruning spring-flowering shrubs: when and how?
   Learn how to prune your spring-flowering shrubs at the right time and in the right way to encourage abundant flowering.

4. When and how to prune bush and shrub roses?
   This article provides specific techniques for pruning roses, essential for generous flowering.

5. Gentle or reasoned pruning of trees
   Discover the principles of gentle pruning, a respectful method to maintain your trees without damaging them.