What Changed?
Tree Selection and Canopy Cover Guide
If you submitted a plan after August 26, 2026, WSSI recommends you revisit your species list to ensure that you are maximizing canopy credit for your project.
- Canopy Credit Species: 114 tree species – a net increase of 10 species – can be planted for canopy credit. Non-native species and uncommon species were removed from the Tree Selection and Canopy Cover Guide and more native species were added.
- Canopy Credit Value: Fairfax County updated the native credit multiplier: species now may qualify for 1.0 to 1.5 credits depending on if they are locally, regionally, or nationally native.
- Fairfax County provided additional information for consideration in plant selection, including updated tree uses and positive and negative traits of tree species.
Critical Root Zone Impacts
Another change to the design side of the development process is that impacts to tree critical root zones must be calculated and shown on the plan set. This change aims to improve and streamline the plan review process for assessing proposed tree impacts. This is not a new concept for development in northern Virginia, as Arlington County has requested this for years now.
Tree Tagging
Further changes to Fairfax County PFM Chapter 12 codify tree tagging as part of the development process; all trees in the inventory must be individually marked in the field with a weatherproof identification tag with the tree number that corresponds to its number on the plan set. This change helps ensure that the correct trees are being removed or receiving protection measures.
Planting Window Update
Fairfax County also expanded the acceptable planting window to October 1 through May 31, so long as the ground is not frozen.
How Do the Changes Impact My Projects?
WSSI’s Urban Foresters and Landscape Architects are available to help you understand the impacts of these changes on your current and future projects. Contact your WSSI project manager or one of our staff listed below.