The Gardeners Almanac

A rule of thumb for almost all flowering shrubs is:

If it flowers before mid-June, prune it after flowering, if it flowers later, prune in late winter or early spring.

Alternatively:

• Spring flowering shrubs straight after flowering.


• Summer flowering shrubs between January and March, before new growth starts.


• Conifers in late Summer of early Autumn.


• Prune flowering evergreens after flowering, and non-flowering evergreens in May.

Overview:

Knowing when and how to prune flowering shrubs is essential, pruning at the wrong time may cost you next year's blooms.

Removing dead, damaged and diseased wood is a matter of good practice, but there are exceptions!

One example is; Shrubs that bloom early in the season usually do so on growth made the previous year, therefore pruning after flowering will allow the maximum time for new growth and the following year's flowers to develop.

Refer to specialist books on pruning particular varieties if you are unsure.

Pruning early-flowering shrubs can be split into two groups; Deciduous and Evergreen.

Deciduous Shrubs:

Shrubs such as Syringa and Hamamelis tend to form a well-branched framework and usually do not need any formal pruning.

However, crossed branches or badly positioned shoots should be removed in late winter when plants are dormant.

Magnolia is an exception, it should be pruned in late summer.

Shrubs such as Philadelphus and Weigela flower on new growth, and can become congested resulting in fewer flowers.

After flowering, prune stems back to strong growth lower down the shrub and remove up to 20% of old, ageing stems back to the base.

With plants such as Kerria, i.e. plants that produce their flowering growth near ground level, remove the flowered stems back to vigorous side shoots, then remove about 30% of the remainder to ground level each year.

Evergreen Shrubs:

Shrubs such as Camellia and Rhododendron tend to form a well-branched framework and usually do not need any formal pruning.

However, crossed branches or badly positioned shoots should be removed in early spring.

Similarly, they should be deadheaded after flowering, although with large plants this may not always be practical.

Shrubs such as Heathers bloom on numerous short shoots during winter and early spring.

Trim back flowered shoots to within 12-25mm (½”-1”) of the previous season's growth to maintain compact neat growth.

Wall-trained shrubs such as Pyracantha are pruned to a permanent framework against a wall or fence.

Plants that are grown for their decorative berries as well as its flowers, e.g. Pyracantha, should have their lateral shoots cut back to two or three leaves, this will also expose the berries.

Remove old fruit the following spring.

Hedges:

To keep the base of a hedge leafy,in spring, taper the sides of the hedge so that so that the top is narrower than the base.

If a hedge is pruned wider at the top than the bottom the lower part will be shaded and the foliage may be quite sparse.

If a hedge is too dense, cut it back to the main stems on one side only, then let the hedge recover for a year, then cut back the other side the following year.

Similarly, if the hedge has become too tall, cut back every second shrub to within a few inches of the ground, allow new shoots growth to sprout for a year,then cut back the remaining shrubs the following year.