Quite often people inquire about pruning this time of the year. This may be due to the fact that the yard doesn't demand much time. Regardless of the reason, pruning is discouraged.
At this time of the year, plants are senescing, visible by changes in leaf color and leaf drop. Certain food products are being moved in the parts of the plant to provide reserves for the winter as well as next season's growth. In addition to storing reserves, all plants are developing various degrees of hardiness in order to withstand the low temperatures in winter. The free water content of cells is dropping while concentrations of sugars and other substances are rising. These substances work on the same principle as antifreeze in car radiators by lowering the freezing point of the water in the plant tissues. This phenomena, called freezing point depression (fpd), allows the plant to withstand sub-freezing temperatures during the winter. However, factors such as fall pruning can interfere with the natural development of plant hardiness.
Pruning stimulates growth very close to the cut. Among other things, pruning stimulates changes in hormone-like substances, called growth regulators as well as the free water content of tissue. Thus, heavy pruning now can reduce, delay or change the natural process of hardiness, making the plant more susceptible to cold injury. For example, severe pruning at this time could stimulate the plant and result in winter injury should we have a severe drop in temperature during the next couple of months.
For most woody plants, the best time to prune is during the late dormant winter season before new growth begins in the spring. One exception is spring flowering shrubs, such as pyracantha or forsythia which should be pruned in spring after the bloom. Many ornamentals are pruned according to their time of flowering. As a general rule, homeowners need not consider pruning their fruit plants until February.