Saturday, November 22, 2008

Nursery and Landscape - Poor Branch Angles Will Lead to Problems Down the Road

Poor branch angles will lead to loss of branches in the future with storms or with heavy snow load. Branches with narrow angles often have ingrown bark at the branch attachment and this results a weak point. This has be a common problem in Bradford Pear. The following is an article on the subject.

Genetic makeup contributes to branch architecture and the angle of attachment in plant species. Branch angle is a predictor of wood strength and a plant’s ability to withstand compromising environmental conditions. Even though the loss of branches may be due to wind or ice load, the genetic predisposition for weak branch or wood strength is the inherent basis for the problem. Common knowledge tells us that vigorous upright branches with narrow attachment angles are prone to storm damage. Horizontal branch angles offer potentially greater wood strength. To ensure the stability and longevity of species with narrow branch angles or multistemmed upright crowns, corrective pruning should be performed on a semiregular schedule. Consider cabling or bracing on plants too old for corrective pruning.

Storm damage to Bradford Pear due to weak branch attachments (narrow branch angles). Photo by Gordon Johnson, UD.

A more intensive approach is to spread branches when plants are very young to achieve a wider branch angle. This is commonly done with fruit trees. Clothes pins on pieces of wood with small nails on both ends can be used and placed to hold the branch away from the main trunk at a wider angle.

Most information from a section of "Abiotic Plant Disorders - Symptoms, Signs and Solutions A Diagnostic Guide to Problem Solving" by Robert E. Schutzki and Bert Cregg, Departments of Horticulture and Forestry, Michigan State University Michigan State University. Go to for the full factsheet with photos.

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