Tree Space Design Highres

T r ee
S pace
D eSi g n
GROWING THE TREE

OUT OF THE BOX

Project Summary:
From 2006 to 2008, Casey Trees convened an advisory group of arborists, urban foresters, landscape
architects and horticulturists to create design standards that will enable trees in urban environments to
survive and thrive, while maintaining sufficient space for pedestrian circulation. Although urban trees facenumerous challenges to growth and development, the advisory group focused on providing trees with
adequate soil volume for root growth and preventing soil compaction.
This report addresses these key issues by presenting (1) a matrix of recommended soil volumes based on
sidewalk width and (2) design options to achieve those soil volumes. Soil volume recommendations range
from 400 cubic feetto more than 1000 cubic feet based on the sidewalk width. Design methods include
open soil areas, covered soil areas and root paths. Although this report addresses the design conditions in
Washington, DC, the recommendations are applicable for any urban area with similar characteristics.

Casey Trees Project Team:
Mark Buscaino, Executive Director
Meredith Upchurch, ASLA, Green InfrastructureDesigner, Project Lead
Heather Whitlow, Director of Planning & Design
Bess Wellborn, ASLA, Planning & Design Fellow

Thank you to our Advisory Group:
Scott Aker, Garden Units Leader, U.S. National Arboretum
Oliver Boehm, Landscape Architect, Michael Baker, Inc.
Robert Corletta, Lead Urban Forester, DDOT Urban Forestry Administration
Jonathan Fitch, Landscape Architect, LandscapeArchitecture Bureau
Steve Genua, System Forester, Pepco Holdings, Inc.
Faye Harwell, FASLA, Landscape Architect, Rhodeside & Harwell
Monica Lear, Deputy Associate Director, DDOT Urban Forestry Administration
Cy Paumier, Urban Design Consultant
Keith Pitchford, Arborist, Pitchford Associates
Elliot Rhodeside, FASLA, Landscape Architect, Rhodeside & Harwell
John Thomas, Associate Director, DDOT UrbanForestry Administration
James Urban, FASLA, Landscape Architect, Urban Trees + Soils

Copyright © 2008 Casey Trees. All rights reserved.
Portions of this report may be reproduced for
education purposes provided that Casey Trees is
acknowledged as the source of the material.

1123 11th Street NW • Washington, DC • 20001
Phone: (202) 833-4010 • Fax: (202) 833-4092 • www.caseytrees.orgTree Space Design: Growing the Tree out of the Box
Contents
Project Summary and Acknowledgements
Overview
Soil Volume: Why is it Important?
Design Methods: How to Achieve Soil Volume
Tree Space: Defining the Terms

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Soil Volume Recommendation
Design Matrix Parameters
Tree Space Design Matrix

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Tree Space Design Examples
All Open Soil Area
All Covered Soil Area
OpenSoil Area Connected to Green Space
Covered Soil Area Connected to Green Space
Combined Open and Covered Soil Areas

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Conclusion

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About Casey Trees:
Casey Trees is a nonprofit organization founded in 2001 to restore, enhance and protect the tree canopy
of the Nation’s Capital. The Planning & Design program within Casey Trees engages and collaborates withgovernment, developers, designers and advocates to ensure that policies, plans and construction techniques
protect existing trees and forests and create spaces capable of supporting large, healthy trees. For more
information, visit: www.caseytrees.org/programs/planning-design.

Overview

Soil Volume: Why is it Important?
A tree’s ability to grow and stay healthy is largely dependent on availablerooting space. This is particularly
evident in highly urbanized areas where many trees exist in small planting spaces with little available soil.
Trees in this situation tend to be short-lived, and most never function as vibrant components of a city’s
infrastructure.
A growing tree will send roots far into the surrounding
soil. In uncompacted soil, the roots of a mature tree
can spread to...