Urban Trees: Why They Need Pruning

By Jeremy Craft, Public Services Division Manager/City Arborist

There are many misconceptions about urban trees and how they differ from trees in the forest or a tree growing in an open park.  Forest and park trees have their own set of challenges; however, not to the extent of trees attempting to survive in an urban environment.  Urban environments and parkways in particular, pose an array of threats that decrease the odds of any tree’s chance at a healthy lifecycle.

Soil conditions, PH levels, light, mechanical effects, and limited growth space are just some of the obstacles that both young and mature trees face while trying to sustain themselves in an urban atmosphere.  This is where Municipal Arborists and trained City staff take action and make a consistent effort to properly care for urban trees.

One primary function City Staff performs is regularly scheduled tree pruning.  Cycle pruning is completed on each City tree once every six years and falls into either one of two categories.  Cycle pruning on young trees (4-8 inches in diameter) is commonly referred to as “Establishment Pruning.”  Establishment pruning is the single most important measure in urban tree care.  It establishes proper form and branch structure, and can lead to an overall cost savings on future maintenance.  Young trees struggle to acclimate to their new sites, especially in urban areas where conditions are not favorable.  Establishment pruning provides a solid foundation for newer trees to experience proper growth habits while adjusting to unfamiliar planting locations.

Cycle pruning on mature trees (greater than 6-8 inches in diameter) requires City Tree Workers to overcome additional challenges.  The trimming of larger trees is initiated from pressure these trees face from their environment that generally come from above the ground.  Factors such as, pests, pathogens, road traffic, man-made structures, other trees, windstorms, and lightning strikes all serve as opportunities to perform pruning maintenance.  In the wild, trees loose limbs to wind and disease frequently, also known as “self-pruning.”  Unfortunately, self-pruning is not advisable in an urban forest, as safety concerns and aesthetic issues most likely will arise.

Rather than letting the trees self-prune, City Tree Crews must take a more proactive approach towards pruning these established landscape trees.  In an urban environment, low hanging branches that interfere with people or vehicles, or block visibility of signs must be removed to facilitate pedestrian and vehicular traffic flows.  Additionally, trees with weak branch unions, crossing branches, dead, dying or diseased limbs and broken limbs all must be trimmed to mitigate the safety concerns that these issues pose.

At times it may appear an excessive amount of limbs are being removed from a tree, but all members of the City’s Urban Forestry Unit are well trained and experienced with proper pruning techniques.  Ultimately, all City trees are pruned with the goal of improving their structural strength, maintaining their health, enhancing their beauty, mitigating risk, and increasing their value.  Landscape trees not only make homes and communities more beautiful, but they also improve our environment and can increase the value of property.