Birch trees are a popular ornamental tree in landscape design, due to their distinctive bark and attractive foliage. When trimming your birch tree, never trim more than 25 percent of the canopy. When the crown of a tree is reduced in size, additional sunlight penetrates the root zone, reducing the moisture in the soil. It also increases the temperature of the soil. Birch trees grow well in moist, cool soil. Bronze birch borers are active from May 1 through August 1 and are attracted to new wounds on a tree. Therefore, trimming should not be done during this time. Plan to trim your birch tree in the fall. The only exception to this would be the removal of dead, diseased or damaged branches.
Trim away dead, diseased or damaged branches as soon as you notice them. Diseased branches should be removed completely and disposed of--do not put them in your compost bin. Dead or damaged branches can be removed at the point of the break or where it connects to the trunk or main branch. Take into consideration how its removal will affect the shape and appearance of the tree. Make a clean cut so that the wound will heal.
View the shape and size of your birch tree from all angles to determine if you need to prune away any branches to maintain its size and shape within your landscape. Look for any branches that may be rubbing on a roof, structure, or interfering with a walkway.
Locate the branch collar (this is on the underside of the branch where it connects to the trunk) and the branch bark ridge (this is on the topside of the branch where it connects to the trunk) of the branch that you are going to prune. Cut right in front of the branch bark ridge and the branch collar, being careful not to cut into the branch collar or branch bark ridge. Also, do not leave a stub; as stubs decay they provide an entryway for disease. Follow this procedure for all of the large branches that you are going to trim from the tree.
Trim away any smaller branches or twigs by cutting it back to a side branch or by trimming it right before the bud. When trimming a small branch or twig before a bud, make a diagonal cut approximately 1/4 inch in front of the bud. Look for low-hanging branches that may be interfering with the clearance underneath the tree.
Visually inspect the crown of your mature tree, looking for any deadwood or crossover branches. Remove the deadwood and crossover branches. If your birch tree is extremely tall, you may want to consider hiring a professional tree service to do this trimming for you. Tree services are not only used to the heights, but they have the proper equipment to perform the job and they are knowledgeable as to what branches to cut to maintain the appearance, health and integrity of your tree.