AMES, Iowa – On Dec. 17, 2016, a large tree fell on a wedding party near Los Angeles, Calif., killing one and injuring several others. While fatalities from falling trees are uncommon, this incident is a worthy reminder of the importance of properly maintaining and pruning trees in urban landscapes.
Trees are widespread throughout this country’s landscape and are often located in public parks or next to sheds and houses in residential areas. While trees provide shade and protection from wind, their close proximity to valuable property and high traffic areas can create hazards if they are not properly maintained.
“Proper tree maintenance begins at an early age for the tree and continues throughout its life, using training methods to promote strong branch unions and canopy structure,” said Gabbi Edwards, urban forestry specialist with Iowa State University Extension and Outreach. “Continual maintenance creates strong and well-balanced canopies, which, in return, decrease the chance of damage from wind, storms and snow.”
As a tree ages, its branches get larger, leading to larger removal wounds. Completely sealing a large wound is difficult and can leave tissue exposed to pests, diseases and rot. If canopy maintenance has not been practiced throughout the life of a tree, starting late is better than not pruning at all.
“Winter is the perfect time to complete a quick evaluation of your tree’s hazard potential since overall canopy structure and form are easier to see than in the summer,” Edwards said. “Be on the lookout for any dead wood, broken, crossing and rubbing, diseased or hanging limbs.
“Another item to be aware of is weak branch unions. Weak branch unions are characterized by the appearance of the branch bark ridge, which is the joining tissue between a branch and the main trunk or stem. The branch bark ridge should be raised and look similar to a mountain ridge across a landscape. If the branch bark ridge seems to be folding inward on itself similar to a fault line, that is a sign of a weak branch union.”
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Weak branch unions can pose a risk of failure at any time throughout the tree’s life. Branches that have weak branch unions with the main stem are perfect candidates for maintenance pruning. Proper pruning techniques are described in ISU Extension and Outreach publication "Pruning Trees: Shade, Flowering, and Conifer" (SUL 5). If a sizable branch needs to be removed or if a branch is a hazard to a building or high traffic area, contact an experienced and insured tree care service to decrease the risk of injury or damage to property.
Falling branches that damage, destroy or injure can often be eliminated before damage occurs by being aware of dead wood, broken branches and weak branch unions. Proper maintenance and pruning promotes a healthier and safer trees for homes and public areas. Take advantage of winter canopy visibility to evaluate trees for potential hazards; removing hazard branches now reduces the risk of failure later.
Photos by Gabbi Edwards.