Sacramento Residents should be Aware of the Phenomenon Known as "Summer Branch Drop" during Periods of Hot Weather

Sacramento, California, July 10, 2006 — During hot, calm summer days—98° Fahrenheit and above, some trees in the City of Sacramento may experience what is known as “Summer Branch Drop,” which results in tree branches or limbs suddenly breaking off and potentially falling to the ground. This phenomenon has been reported throughout the United States and other parts of the world.

Although no scientific explanation is apparent, many arborists believe the phenomenon is caused by water stress. Branches that break are usually more horizontal than vertical, extending to the tree crown or beyond. In addition, the breaks usually occur at a point away from where the limb attaches to the trunk. The wood at this location often appears sound and healthy, making it difficult to accurately predict breakage.

Summer Branch Drop affects primarily older, mature trees. In the City of Sacramento, tree species susceptible to the phenomenon include Ash, Elm, Eucalyptus, Oak, Maple, and Plane.

According to Joe Benassini, Urban Forestry Manager, City of Sacramento Department of Parks and Recreation, “affected trees do not seem to exhibit any signs of a problem prior to a failure. By nature, it is frustrating to urban foresters due to our lack of ability to predict and prevent these events. While we all love the much needed shade this time of year, especially from our largest of trees, residents and the public should be cautious, particularly where previous failures have occurred.”

Sacramento residents and others who have occasion to be near tree-shaded areas should plan events accordingly and exercise caution when located directly beneath large, mature canopies, especially during very hot summer days.

City resident’s can call Urban Forest Services at 808-6345, or the City Operator at 264-5011, to report broken or hanging branches on City trees.

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