RHS Pruning Group 10 – Evergreen Shrubs

Overview

RHS Pruning Group 10 covers a range of evergreen and semi-evergreen shrubs, many of which are relatively compact plants such as lavender, heather, thyme and santolina. The group includes plants that flower on the previous year's growth in spring or early summer, as well as plants that flower on the current year's growth later in summer or autumn.

Unlike shrubs that require substantial annual pruning, plants in Group 10 are generally pruned to remove spent flowering growth, encourage compact new growth and prevent plants becoming woody, straggly or untidy.

This is particularly important for plants such as lavender. Regular light pruning can help maintain a dense, attractive shape, whereas allowing plants to become increasingly woody can make them much more difficult to rejuvenate successfully.

Timing is important because it depends partly on when the individual plant flowers. Shrubs flowering on growth made during the previous year are normally pruned immediately after flowering. Those flowering on the current season's growth are generally pruned in early to mid-spring.

The basic principle behind RHS Pruning Group 10 is:

Regular light pruning keeps evergreen shrubs compact, healthy and productive – but avoid cutting unnecessarily into old, bare wood.

Which type of plants are suitable to prune with Pruning Group 10?

RHS Pruning Group 10 primarily includes evergreen shrubs that benefit from regular trimming after flowering or during spring, depending upon their flowering habit.

Typical examples include:

  • Calluna – heather

  • Erica – heath

  • Helianthemum – rock rose

  • Hyssopus – hyssop

  • Lavandula – lavender

  • Ruta – rue

  • Santolina – cotton lavender

  • Thymus – thyme

  • Ulex – gorse

  • Bouvardia

The RHS also includes some deciduous shrubs within Group 10, including Potentilla fruticosa (now generally classified as Dasiphora fruticosa) and Ceratostigma willmottianum.

Many Group 10 plants are naturally relatively compact and are valued not only for their flowers but also for their evergreen foliage, fragrance, texture and ability to provide year-round structure.

Lavandula is perhaps one of the most familiar examples. Regular pruning helps maintain the characteristic compact mound of foliage and reduces the tendency for plants to develop long, woody stems with foliage concentrated towards their ends.

Calluna and Erica can similarly become increasingly open and woody if never pruned. Light trimming after flowering helps maintain a denser, more attractive plant.

Santolina and Helianthemum also benefit from regular attention to prevent plants becoming excessively loose or straggly.

The important consideration with many of these shrubs is that they may not regenerate reliably from old, leafless wood. Pruning little and regularly is therefore generally preferable to allowing a plant to become overgrown and then attempting to rejuvenate it with severe pruning.

How to prune plants in RHS Pruning Group 10

The aim when pruning Group 10 shrubs is generally to remove flowered growth while retaining a healthy framework of leafy stems.

The RHS recommends cutting shoots that have flowered back to around 1.5–2.5cm (¾–1in) from the previous year's growth.

Begin by inspecting the plant and removing any dead, damaged or diseased growth.

Then:

  • Remove spent flowers and flower stalks.

  • Shorten shoots that have flowered.

  • Trim back excessively long or untidy growth.

  • Remove weak or badly positioned stems.

  • Maintain a compact, balanced shape.

  • Keep pruning cuts within healthy, leafy growth wherever possible.

  • Avoid cutting unnecessarily into old, bare wood.

The last point is particularly important with lavender. Established lavender plants can become woody at their bases, and cutting deeply into old stems where there are no healthy leaves or shoots can leave areas that fail to regenerate.

The RHS specifically advises avoiding cutting lavender back into old wood.

Instead, regular annual pruning should aim to maintain foliage lower down the stems, reducing the development of a large woody framework in the first place.

With heathers, lightly trim over the plant after flowering, removing the old flower heads and a small amount of the accompanying growth. The objective is to encourage a compact mound rather than cutting the plant severely back into its woody centre.

Similarly, plants such as Santolina and Thymus can be lightly trimmed to retain a dense, neat form.

Young plants can also benefit from having their growing tips pinched or lightly trimmed to encourage branching and create a bushier framework.

Always use clean, sharp secateurs or shears. For small-leaved plants grown as compact mounds, shears can be particularly useful for achieving an even finish.

When should I prune plants in RHS Pruning Group 10?

The correct time to prune RHS Pruning Group 10 depends upon when the individual shrub flowers and whether those flowers are produced on old or new growth.

For plants that flower in spring or early summer on growth produced during the previous year, pruning should generally take place immediately after flowering.

This allows you to enjoy the current flowering display before removing the spent shoots and gives the plant sufficient time to produce healthy replacement growth.

For shrubs that flower in late summer or autumn on growth produced during the current year, pruning is generally carried out during early to mid-spring.

Lavender requires slightly more specific treatment. Once flowering has finished, deadheading and trimming can help prevent plants becoming straggly. The RHS notes that late-summer trimming is useful but advises against autumn pruning in colder or wetter areas, as this can leave plants more vulnerable to winter damage.

This is particularly relevant in cooler and wetter parts of the UK, where pruning too late in the season can leave fresh cuts and young growth exposed to prolonged winter conditions.

Dead, damaged or diseased material can be removed whenever necessary, but substantial trimming should be carried out according to the requirements of the individual plant.

The easiest way to remember RHS Pruning Group 10 is:

Trim regularly, prune after flowering where appropriate, and don't cut deeply into old wood.

Regular, relatively light pruning is generally much more successful than occasional severe pruning. By keeping plants compact from an early age, Group 10 shrubs such as lavender, heather, thyme and santolina can retain their attractive shape, produce healthy flowering growth and avoid developing the bare, woody centres often seen in neglected specimens.