If you have to prune, do not ‘snip and clip’ indiscriminately. Most ornamental trees require no pruning other than the removal of unwanted branches growing on a bare trunk, especially where the tree has been top-grafted, and the taking out of badly placed and rubbing branches and dead and diseased wood. These should be removed completely, leaving no snags or stumps.
Conifers not used for hedging purposes need not be pruned except to remove pieces which have grown out of shape, but sometimes an all-over trim will improve the colour and form. You should choose subjects which will only grow to the size you want them to, not try to cut them to fit the hole!
The majority of shrubs, unlike roses, do not deteriorate greatly without regular pruning, although if they are never touched they will eventually get into a bit of a tangle, and end up woody and leggy. (Do not forget to use clean, sharp secateurs and make a sloping cut just above a bud or eye.)
For pruning purposes shrubs can be divided into 4 categories:
- Evergreens. No pruning is necessary except light shaping if required, and the removal of dead and diseased wood, preferably in late spring or August. Some can be cut hard back in spring if necessary (but not conifers).
- Shrubs flowering on old wood produced the previous season. These are mainly spring-flowering shrubs. Remove all old flowered wood after flowering, and badly placed branches, also dead and diseased growths.
- Shrubs flowering on old and new wood. These are the early summer-flowering ones. After flowering, remove completely some old flowered branches and shorten back some of the younger stems to fresh growths on the main branches. Thin out crowded growth and remove weak, dead and diseased stems.
- Shrubs flowering on the current season’s wood. These are mainly the late summer-and autumn-flowering ones. Cut back to within two or three buds of the base or of the main branch framework in early spring.
This method of pruning is also used for shrubs grown mainly for their coloured stems in winter, and also for some quick-growing deciduous ones planted for the colour of their young foliage.
Note. Research has proved that treating the cut surfaces with a pruning paint is unnecessary.