Clearance Pruning Tips – Raise tree canopies along with your program’s credibility

As suggested in last month’s installment of Timely Tree Tips, winter is a great time to prune trees. While you’re out there pruning, it’s also a good time to evaluate trees in high-traffic areas, such as downtown, commercial zones, or arterial streets and boulevards, for any traffic sign visibility or clearance issues that low-hanging or over-reaching tree limbs may present.

Trees are especially important for air quality and attracting customers in densely developed, heavily used areas. However, these growing environments inherently lead to tree-related conflicts with traffic signage, commercial signage, lighting, and line-of-sight visibility at corners and driveways. Such conflicts can create serious safety issues if left unaddressed, as well as damage to trees whose limbs may be smashed, broken, torn, or even hacked off by someone taking the issue into their own hands. Be proactive: pay attention to these issues as they arise and prune your trees properly! Your trees will thank you for it, and so will pedestrians, truck drivers, metro bus drivers, street-sweepers, the local police department, the city’s public works department, and local businesses.

Resolving tree issues before they happen raises the visibility and credibility of your program, your staff, your tree commission, volunteers, and others who have an impact on tree pruning in your city. The actual pruning activity will be a function of the clearance needs, tree species and size, tree location relative to other objects, your community’s thresholds for risk, and your available staff and budget to accomplish the work. Urban & Community Forestry staff at the Department of Natural Resources recommend the following clear zones, based on industry standards, as general guidance for clearance pruning:

  • 14′ of clearance over streets
  • 8′ of clearance over sidewalks
  • Minimum clearances traffic signs and signals so that they are completely visible when the tree is in leaf

Here are some tips to help you triage your pruning needs and accomplish the work:

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1. Always have your trees pruned by an ISA Certified Arborist who is familiar with industry best practices and standard pruning techniques. Consider having your staff participate in the ISA certification program to build in-house skills and for greater community confidence in your staff’s tree work.

2.  Work with Public Works staff to identify the high-traffic areas of your community where you believe concerns about traffic sign and tree limb clearance may be greatest.

3. Visit the identified locations, noting pruning needs as a basis for the work order.  Be sure to add this work into your city’s street tree inventory tracking system.

4. Walk up and down the sidewalks to identify low limbs that may be interfering with pedestrian traffic, and locations where streetlights may blocked by tree foliage. Travelling on foot also offers the opportunity to observe the clearance between tree limbs over the street and the tops of passing vehicles.

5. Drive the same streets in a car to scan for obscured traffic signs and signals or limited visibility at intersections. Pick-up trucks, SUVs, and other large vehicles tend to have better visibility due to their height. If you can identify visibility issues in a lower vehicle, you are more likely to resolve those issues for more drivers.

6. If your community has traffic cameras or radar-triggered speed limit warning signs, work with the local police department to help you identify locations where trees may be obscuring the camera’s field of view or the radar’s projection.

7. Contact your local utility provider if tree limbs are conflicting with overhead power lines. DO NOT attempt to prune tree limbs near overhead utility lines!

8. Establish a regular 3-to 5-year inspection and pruning cycle for trees in these highly visible locations in your city. Routine vegetation maintenance in these important landscapes is a wise investment for you, your tree program, and your community, and it may help you build support for enhanced program funding.