Reasons for pruning include: removing dead or diseased branches, branches that rub together, keeping your plants at a manageable size, to encourage fruiting or flowering, to open up walkways and to keep trees and shrubs from touching your house or car. Assuming your trees and shrubs are already established on your property, stand back and take an imaginative look at how they are growing. Are they growing sideways or touching anything? Are they growing way too tall and too fast? Is there a lot of dead growth or branches that need to pruned away? Picture what they might look like after you cut here, or there. Then do it.
During the winter, while the plants are dormant, pruning is a safe bet, but maybe you should wait until after the spring flowering trees and shrubs finish blooming. These may include azaleas, flowering plumb or cherry, forsythia, lilac, magnolia and spirea. Shrubs grown primarily for their foliage should be pruned in early spring, before growth begins. These include barberry, burning bush, honeysuckle, ninebark and smokebush. Also prune in early spring, roses, clematis and hydrangeas.
Tips for pruning to help avoid certain diseases include; DO NOT prune oaks during April, May or June but DO prune honey locust while dormant during late winter to avoid stem cankers. February through early April go after your apples, flowering crabapples, mountain ash, hawthorns and cotoneasters. Trees that bleed, such as maples, box elder, walnut, birch and ironwood should be pruned a little later, like late spring or early summer, after the leaves fully expand. Bleeding trees are really not as big problem as you might think.
Dormant oil, applied during the winter, is your best defense against insects that attack your plants during the summer. Spray your plants when the temperature rises to around 50 degrees or warmer and will remain between 50 and 65 for at least a couple of days. It is best to spray just before the buds on your trees and shrubs start to swell.
You can buy a commercially sold oil spray, or make your own mix: 1 quart mineral oil, 1 quarter pound oil-based soap with 8 ounces of water. Bring to a boil then mix 1 part solution to 5 parts water and spray immediately as the mixture can separate quickly.