Our Portland area is known for its lush urban forest. We gratefully live amongst trees here. Trees and shrubs grow above and around our houses and workplaces. We walk in their shade along sidewalks and on turf. We drive cars and ride bikes under their canopy on the roadways. Caring for urban trees often requires clearance pruning, which removes growth that may infringe on these structures and areas.
Plant to Avoid Infringement
Consider the tree growth habit when selecting a tree to plant in the location. Planting trees with a more upright growth habit will minimize the need to clearance prune for height clearance. Accounting for a tree’s ultimate canopy height and spread at planting time will reduce the need for clearance pruning throughout the tree’s life.
Clearance Pruning for Structures
Trees and shrubs growing unchecked near structures can rub against gutters, roofs, fences, and siding, causing structural damage as well as damage to the plant. The camellia seen above is growing under an eave and next to a structure and must be clearance pruned from above and the side.
Generally we recommend the selective pruning of small tree growth within 3 feet over a roof and large tree growth within 10 feet over a roof. In addition to reducing the likelihood of structural damage from swaying branches, the increased sunlight to the roof will reduce roof moss growth. Our arborists are well-versed in technical rigging procedures that allow for safe, controlled lowering of removed branches near structures.
Clearance Pruning for Streets and Sidewalks
The urban forestry departments of many local municipalities define tree canopy clearances for streets and sidewalks to allow for safe pedestrian and traffic passage and visibility. For example, the city of Portland requires that trees have a clearance of 7 1/2 feet above sidewalks, 11 feet above residential streets and 14 feet above arterial streets.
In addition to presenting a hazard to passing traffic, low tree branches over streets are at risk of damage from tall passing vehicles. Clearance pruning over thoroughfares raises the canopy of the tree by removing low growth using proper pruning cuts. This minimizes the hazard to passing traffic and minimizes further damage to the tree from insect or disease infestation that may occur due to a ragged break caused by a passing vehicle.
Clearance Pruning for Other Plants
Trees and shrubs planted in close proximity are competing for the same nutrients, water, and sunlight. Large or fast-growing plants may outcompete their small or slow-growing neighbors for these resources. Larger plants may need to be clearance pruned to allow sunlight to reach the smaller plants and allow them to thrive.
When Is Clearance Pruning Not The Answer?
If a tree or shrub is planted too closely to a structure or thoroughfare, no amount of clearance pruning will be able to correct for the poor location. Aggressively clearance pruning a tree on one side compromises aesthetics, and in extreme cases increases the likelihood of breakage and even toppling. Regrettably in these situations, removal is often the best option.
Clearance Pruning Best Practices
The recommended frequency of clearance pruning will depend on the growth rate of the species and its planted proximity to structures, thoroughfares and other trees. Our certified arborists can make recommendations for clearance pruning distance and frequency during your free estimate.