Trees complete the street

Ash tree planted in transit island on Dexter Ave N

Planting a tree with a root ball weighing over eight hundred pounds on a busy arterial is not an easy task, but the SDOT Urban Forestry landscape crew was up to the challenge.  Through careful planning and creative problem-solving, the planting went smoothly, with only occasional interruptions to bike lane traffic and little impact to vehicles.  How did they plant these oversized trees without a crane or loader?  Senior Gardener Christina Orrino suggested a method called “root washing,” in which water is used to remove most of the soil from the root ball.  This enables the planters to inspect and remove damaged or circling roots that can cause problems as the tree grows.  “Root washing” is an accepted planting method and may help the tree establish a healthy, stable root system.   Removing the soil drastically reduced the weight of the root ball; the result was a safer and less expensive project. 

The four Cimmaron Ash trees (Fraxinus pennsylvanica ‘Cimmzam’) were planted in transit islands constructed on Dexter Avenue North as part of an SDOT Arterial Asphalt and Concrete (AAC) paving project.  Larger than standard size trees were selected for their form and ascending branch habit  to enhance visibility and ensure street clearance.  The SDOT Urban Forestry Landscape Architect, Shane DeWald credits the Dexter Avenue Project Managers and Project Engineer for their support for trees. They provided the opportunity to include street trees as a component of the Dexter bus islands.  This is one of many examples of SDOT teamwork to expand Seattle’s urban forest canopy cover, providing shade for the transit islands, among other environmental benefits. The planting concludes the AAC project, adding the environmental element to create a ‘complete street.’  

More info on root washing: http://www.newenglandisa.org/PlantingTreesTheRootWashingWayJimFlott.pdf