There is a mistaken belief in some quarters that all shrubs must be pruned at one period of the year or another. This is entirely untrue. Shrubs may be grown without anyat all, especially in gardens where there is plenty of room. On the other hand, there is need in nearly all cases to cut out dead wood, to remove crossing branches, to remove branches that are rubbing one another, and to cut out weak wood. Such pruning has been described as a ‘sanitary operation’, i.e. the removal of the diseased and dead wood prevents further infection, and the out of the crossing branches lets in more light and air and so helps to ensure better ripened wood and in consequence more beautiful blossoms and berries.
In smaller gardens there is need as a rule to carry out a certain amount of pruning each season to prevent shrubs overgrowing the space which has been allowed for them. Naturally this general shortening back of the branches encourages the production of new wood in its place, and in many cases this wood will be particularly floriferous. Much of the pruning in the normal way may be done in the winter. Then it is possible to cut out a large branch to a point just above a younger and smaller one which can be left growing in approximately the same direction, and by making the cut just above the lower branch, it can be ensured that there is no dead end or snag of wood left which will die back and may cause the entry of disease.
On the whole it is better to aim at pruning soon after flowering takes place. This allows the new growths to develop and to be ready for flowering the following season at the right time of the year. The shrubs which flower on the wood made the previous year there, must always be pruned as soon after flowering as possible, for this is the only way of allowing sufficient time for the shrub to produce its blossom buds for the following year. The shrubs which flower on the new or unripened wood produced that very season are generally pruned in the spring, rather than immediately after flowering, for if the pruning is done too early, new growths tend to be made immediately and these may be too soft for a hard winter, and so be killed.
Putting it another way, it can be said that the shrubs that flower from June onwards on the current season’s growth should be pruned back in the winter, while the shrubs which flower in the spring or early summer on the growths made the previous year should be pruned in the summer immediately after flowering. This group is the one into which the majority of the hardy shrubs fall. It is largely for this reason that the only pruning most gardeners do to them is the thinning out and this need never be anoperation.
It is customary to treat certain shrubs rather differently. For instance, thegenerally has all its young shoots shortened close back to the main early each season with the result that it produces long pendulous growths which bear the best blooms in the summer. The cutting back is aimed at producing very vigorous young growths. That lovely spiram Anthony Waterer, for instance, gives a wonderful show when the shrub is cut back almost to the ground in the early spring. paniculata should be treated in a similar manner and so should Spircsa japonica.
Some shrubs are grown for the beautiful winter colours on the. These are usually pruned before the sap starts to rise in the spring, almost to ground level, and thus long, strong growths are produced during the season which give the yellow or red winter colour to the border. The Dogwoods and Willows are typical examples of this type of shrub.
Learn to appreciate first of all the normal size of the shrub concerned, then its habit of growth and lastly whether it is a slow or quick grower. These three things will help to give you the clue to the pruning that is desirable. The slow growers for instance, need very little attention at all; the quick growers may need regular attention especially after they have grown a good size. The heaths do not like being cut back when they are old and yet are apt to get a little leggy and so the dwarf plants often need pruning in the young stages to keep them stocky. The lovely Magnolia, on the other hand, which makes a large shrub, hates being pruned at all, and must be allowed to develop at will.
Use a very sharp knife when pruning or a first-class pair of secateurs. If any really large cuts have to be made with the saw, these should be pared over afterwards with the knife, to leave the wounds smooth, and then a painting should be given with a thick white lead paint.