Trimming your trees can be easy if the tree is on the small side, but trimming a large tree can be a big job and possibly dangerous work that you should leave to a professional arborist. Cutting off dead and diseased branches is a good idea for all trees. You can help to shape trees into attractive forms when you trim them properly at the right time of year.
Gather the materials you will need to trim your tree. Wearing goggles or other protective eyeware is wise, as are garden gloves. If you have a large tree, make sure your ladder is in good, safe condition. Sharpen your tree saw or chain saw and plan for how you're going to dispose of the branches you cut.
Cut Back to the Branch Collar
Whenever you cut off a tree branch, always cut as close to the trunk as you can without cutting into the trunk itself or the "branch collar" where the branch grows from the trunk. The collar is usually a slightly bulbous area where the branch connects to the trunk. You can make sure you're cutting each branch correctly by making your cut about one inch from the outside edge of the collar.
Choose Your Tool
Use garden loppers or a manual tree saw for cutting small branches. You might need to use a chain saw for larger branches, but always be very careful when you use this tool, especially if you must do so while you're on a ladder. Tree branches can be quite heavy, so clear any tools, pets, people, patio furniture and so forth from the area under your cutting area.
Cut Off Dead and Touching Branches and Water Sprouts
Start your trimming activities by cutting off any dead branches, remembering that some trees are deciduous and can look dead during winter. Cut any branches that bump into other branches or that are misshapen. Also cut off all water sprouts, which grow out of the tree's base and take energy away from the tree.
When Not to Trim Your Tree
Avoid trimming any tree when it is in flower and when it has fruit on it. Unless the tree is an invasive species that you do not want to spread its seeds, leave your tree trimming to winter, when trees are dormant. Trim oak trees only in winter, because doing so from spring through fall can make them susceptible to a fungal wilt disease.
To Tar or Not to Tar
Some people believe pruning tar is helpful to seal out moisture and the possibility of diseases that might enter your tree through the cut areas, but another school of thought says that this tar can actually seal in insect pests or diseases. Speak to a knowledgeable staff member at your local nursery to get an educated opinion about the use of such products. Some professional landscapers and gardeners say that the wounds caused by trimming a tree will heal by themselves.