Tree Lovers’ Dream Project: Arlington County Street Tree Inventory

By Kathy Philpott Costa

On March 13, a group of volunteers made up of Arlington Master Naturalists, Tree Stewards and Americorps members met with Arlington County Forester Vincent Verweij for basic training on how to conduct a street tree inventory. These volunteers will soon contribute to an ambitious project to update information on more than 21,000 street trees in Arlington County–including more than 1,000 empty planting spots–in its database.

The County’s street trees are those that have been designated as County-owned and are in a County right-of-way, or along the edge of streets and sidewalks.  Trees on private, federal or state property are not Arlington “street trees.”  Volunteers were interested to learn that Arlington County’s ownership of its street trees stands in contrast to much of Virginia, where the Virginia Department of Transportation owns and maintains most spaces adjacent to streets.  Needless to say, local ownership leaves the County with an overwhelming responsibility to maintain its trees and plant new ones where old ones are removed.

Vincent Verweij estimates that to complete a full inventory will require a total of 100 full workdays or 200 half-days of assessment and database updating. The group of enthusiastic volunteers learned how to use an ArcGIS (interactive mapping) program on an iPad to update this inventory.  Each participating volunteer will be assigned a portion of the Arlington County map and will walk the streets in that area to assess the trees. The ArcGIS program already has most of the County’s street trees mapped and identified, and volunteers will confirm and input information on each tree’s species, size, health, planting site, and other details helpful in assessing the tree’s future and suitability for its location.

Most of the tree information in the County’s database has not been updated for close to ten years.  A current inventory will allow the County to assess how its urban canopy species makeup is changing over time, understand the average health of its street trees, pinpoint where there might be biodiversity or invasive species problems, and determine which species might be best or worst suited to certain locations.  The County sees an additional benefit in having a shareable, up-to-date database that can aid in planning regional tree care programs and increase efficiencies across the County and within the larger surrounding region.

Stay tuned for more updates as volunteers organize themselves and spread out to take on this project.  To volunteer and learn more about the tree inventory project, contact  Arlington County Forester Vicent Verweij at

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