Pruning Trees and Shrubs – How to Prune Shrubs


Pruning Trees and Shrubs

pruning shrubs

Shrubs usually need more pruning than trees and I shall start by discussing shrub pruning.


Reasons for Pruning Shrubs

The main reasons for pruning shrubs are to encourage the formation of flowers and in some cases fruits; to ensure that the plants remain healthy and vigorous, and to keep them shapely. Some shrubs do not require any pruning; for example, evergreens such as conifers, rhododendrons and azaleas.

On the other hand, if those shrubs which benefit from pruning do not receive such attention they will deteriorate rapidly within a few years and will certainly not flower as well as they should do. I don’t like to see pruning carried out in a haphazard way, just for the sake of doing it. It is essential that you should become familiar with the habits of growth and flowering of your shrubs and prune them accordingly – you must know which ones need pruning and which ones don’t.


Maintaining their Shape

Another important point when pruning, is to try to maintain the shrub’s natural shape. How often do we see shrubs being clipped hard all over by gardeners who know little or nothing about pruning, just to keep them looking neat and tidy. This invariably prevents them from flowering because in the process the flower producing wood is removed.


When to Prune Shrubs

Deciduous shrubs can be divided into two groups for the purpose of pruning.

Those that flower in the spring or early summer produce their blooms on growths formed in the previous year. These are pruned immediately after flowering has finished to give them a chance to make new growths during the summer and autumn. These new shoots will then produce flowers the following year.

The second group comprises shrubs which flower during the summer and autumn. Many of these produce their blooms on growths which are formed in the current season during the spring. These kinds are pruned very hard in March or April to encourage plenty of young shoots to form, so ensuring an abundance of large flowers later in the year.

With evergreen shrubs pruning is confined to the shortening of growth to ensure shapeliness, when this is necessary, and the removal of dead  or weakly growth.


How to Prune Shrubs

First, let us consider those shrubs that flower in the spring and early summer on the previous year’s wood.

These include chaenomeles, cytisus or brooms, deutzia, Jasmimum mudiflorum, kerrias, philadelphus, Prunus triloba, Spiraea arguta, S. prunifolia plena,  S.thunbergii and weigelas. The stems that have flowered are cut back to young shoots lower down the stems.  There are usually two or three of these shoots which will develop and bear flowers in the following year.

pruning shrubs

Forsythias flower on shoots which are two years old or more but these are pruned in the same way after flowering.

When pruning brooms, all the stems with developing seed pods are cut back to young shoots. With weigelas and deutzias, cut out the old flowered wood near to the base of the plant, at the same time leaving as many new shoots as possible. They will flower much better for this harder pruning.

We come now to the shrubs which flower on the current season’s wood. The main ones to include here are Buddleia davidii, caryopteris, deciduous varieties of ceanothus, hardy fuchsias, Hydrangea paniculata, and tamarix. I always cut all the old stems down to within a few inches of the ground in early spring. These shrubs are very vigorous and soon send up plenty of young shoots.

When Buddleia davidii, Hydrangea paniculata, ceanothus and tamarix are cut right down each year, they do not grow quite as large as they would do naturally. While this suits owners of small gardens admirably, some gardeners like to have larger specimens. Therefore, a framework of older branches can be built up by pruning some of the shoots less severely.

However, hard pruning of the flowered wood must still be carried out. The flowered shoots contained on the main framework must be cut back to within two or three buds of the main stems during March or April.

Those shrubs which are grown for the beauty of their coloured stems should be cut down to within an inch or two of the ground in early spring each year. They will then send up masses of whispy shoots. This is a good way, for example, of growing willows in a smallish garden. The coloured-leaved elders can also be pruned hard each spring, either to within a few inches of the ground, or a framework of older wood can be built up and the shoots from this cut back to within two or three buds of their base.

After pruning those shrubs which flower on the current year’s wood, I usually give them a dressing of an all-purpose fertiliser. I find that this encourages them to make strong growth.


Deadheading – Removing Dead Flower Heads

deadheading pruning shrubs Certain shrubs, especially some of the evergreens, require no more in the way of pruning than the removal of dead flower heads. It is best to remove them as soon as the blooms have finished, before the seed pods are properly formed, as seed production wastes the plants energy and will mean fewer flowers in the following year.

With rhododendrons and azaleas I twist off the clusters of seed pods, taking care not to damage the buds which are developing just below. I remove the old flower heads of lilacs with a pair of secateurs, cutting them off at their base.

I give my heathers and lavenders a light trim with a pair of shears after they have fiowered – this also keeps them compact. I trim them just sufficiently to remove the dead flowers and never cut into the main shoots or old wood. The winter-flowering heathers I usually leave until March or April before trimming them over.


Cutting out Suckers

Some shrubs which have been budded or grafted on to a rootstock, invariably throw up sucker growths from the stock. The main shrubs which come into this category include rhododendrons, azaleas and lilacs. I remove the suckers by cutting them out at their point of origin. They are easily identified as the leaves are usually slightly different from those of the main growth.


Removing Dead Wood

I always keep an eye open for any dead or diseased wood in shrubs and remove this regularly. Dead wood offers an open invitation to diseases and it is, of course, unsightly. For both reasons it should be removed without delay. The need for the removal of diseased wood needs no explanation.

During the spring I also cast an eye over my shrub roses for dead wood. At the same time I remove a little of the very old wood, especially if the bushes are becoming congested. Apart from this, shrub roses need little attention with regard to pruning.


08. August 2010 by Dave Pinkney
Categories: Plants & Trees, Pruning | Tags: , | Comments Off on Pruning Trees and Shrubs – How to Prune Shrubs

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