Although some plants can be pruned at almost any time of the year, in general this is far from being the case and often timing is critical if the desired result is to be achieved. The main pruning period for many plants, including roses, soft fruits, and many tree fruits, is the dormant season, from late autumn to early spring. However, winter pruning stimulates growth whereas summer pruning checks it. Most of the pruning to form the spur systems of restricted forms of fruit trees, such as cordons and espaliers, is carried out in summer to avoid promoting unmanageable growth.
Summer pruning of hedges puts the perfect finishing touch on a garden and creates an attractive boundary. Cutting a hedge regularly maintains its shape and avoids problems with unwanted shade. A regular pruning regime makes it easier to control hedges. As with most garden maintenance, cutting regularly makes things much easier than leaving maintenance until the hedge has taken over the garden. Most evergreen hedges require trimming a couple of times during the growing season. Conifers need particularly regular attention due to their fast growth. In comparison, maintenance of informal hedges is determined by when they flower.
The full ornamental potential of many plants can only be realized by pruning at an appropriate time and must take account of the age of the wood that bears flowers, the most decorative foliage, or the most vividly colored stems. Many shrubs that flower in the spring do so most prolifically on one-year-old wood. Cutting out the oldest wood when summer pruning after flowering will encourage the development of replacement shoots that will flower the following year. Shrubs and climbers that flower on the current seasons’ wood are best pruned in early spring, with the previous years’ wood being cut back to a low framework of branches.
In the case of some plants that are susceptible to particular diseases, the risk of infection can be reduced by pruning when they are least vulnerable. Silverleaf is a serious fungal disease of plums and other stone fruits and also of some ornamentals. The windborne spores, which gain entry to the plant through fresh wounds, including pruning cuts, are released by the fruiting bodies of the fungus from early autumn to late spring. Summer pruning greatly lessens the risk of infection.