Photo Credit: Gemma Grace / CC BY-NC 2.0

By Michael James

Ontario’s forestry community has played a significant role in the development of the discipline we recognize the world over as “Urban Forestry.” In fact, the origin of the term “Urban Forestry” as it is known and applied today came from within Ontario’s borders, when it was first employed [1] by Dr. Erik Jorgensen in 1965 while he was faculty at the University of Toronto. He coined the term in order to name the program for a graduate student who was studying aspects of trees in the City of Toronto. Jorgensen first defined the term in writing in 1967: “A specialized branch of forestry that has as its objectives the cultivation and management of trees for their present and potential contribution to the physiological, sociological and economic well-being of urban society. These contributions include the over-all ameliorating effect of trees on their environment, as well as their recreational and general amenity value.” [2] [3]

Today, the cultivation and management of the urban forest is highly influenced by space restrictions in urban sites, where it can be difficult to provide large planters for trees that would give them the soil volume they need to reach maturity. This challenge sometimes leads designers, developers, or planners to simply ignore the soil needs of the trees and plant them in small openings that ensure a short lifespan. Now, however, policy is beginning to play a significant role by requiring planners and designers to meet minimum soil volume requirements for trees on their projects, and Ontario is a front runner in Canada and globally in this effort.

From Oakville to Toronto, Ontario municipalities are recognizing the need to approach the planning, planting, and care of trees as a form of infrastructure that has a big impact of the sustainability, health, and wellbeing of urban communities. Soil volume requirements that guarantee trees’ access to a minimum amount of growing media are at the core of this effort. To date, five municipalities in Ontario have implemented soil volume standards, more than any other province in Canada.

In the words Allan Elgar, Councillor for the City of Oakville who lead the effort to implement Oakville’s soil volume standard: “Either you provide the requisite volumes, or you don’t get to build. People need to understand that we’re treating this like water, pipes, or any other type of infrastructure. Now it’s just one more tool in the toolbox.”[4] In light of this policy-driven commitment to providing favorable conditions to trees, we predict that in 25 years Ontario will have one of the most impressive urban forests in North America.

Below is a list of those municipalities in Ontario who are pioneering, in Jorgensen’s words, “the cultivation and management of trees for their present and potential contribution to the physiological, sociological and economic well-being of urban society.” [5]

Medium tree: 18 m3 (dedicated or shared)
Large tree: 50 m3
Notes: Applies to all streets in the Planting & Furnishing Zone (located between the sidewalk and the edge zone and provides an additional buffer between vehicles and pedestrians)
Official Document: Downtown Guelph Streetscape Manual, Built Form Standards and St. George’s Square Concept

Small tree (20 cm): 17m3 if single, or 11m3 if shared
Medium tree (greater or equal to 40cm): 28m3 if single, 18.5m3 if shared
Large tree (greater or equal to 60cm): 45m3 if single, 30m3 if shared
Official Document: Urban Forest Details – Tree Planting & Establishment Best Management Practices (Appendix C of Development Manual)

Small tree: 15 m3 (530 ft3)
Medium tree: 23m3 (812 ft3)
Large tree: 30 m3 (1,059 ft3), if single, or 15 m3 (530 ft 3) if shared
Notes: Minimum soil volume for tree planting in a parking lot island is 15 m3 (530 cubic feet).
Official Document: Markham, Ontario Trees for Tomorrow: Streetscape Manual

30m3 (1,059 ft3) of soil per tree, or 15 m3 (530 ft3) if in a shared planting trench
Additional information about the standard in this interview with Oakville Councillor Allan Elgar

Minimum of 20 m3 (706 ft3) of high quality soil per tree if in a shared planter, and a minimum of 30 m3 (1,059 ft3) of soil per tree if in a single planter
Official Document: 2014 Update Highlights* to Toronto Green Standard
*In 2014, the minimum shared soil volume increased from 15m3 to 20m3 following research and on-site calculations that determined need for increase in order to reach city’s 40% canopy target.

York Region (currently in trial period)
Minimum of 30m3 per tree
Notes: This soil volume standard is part of the York region’s new Sustainability Matrix, which is currently in a trial period before it becomes official.
Official Document: Measuring the Sustainability Performance of New Development FINAL COMPREHENSIVE REPORT

[1] Technically, the term “Urban Forestry” itself was first used in 1894 by G.R. Cook in “Report of the general superintendent of parks. Second Annual Report of the Board of Park Commissioners, Cambridge, Massachusetts,” but it is unlikely that Jorgensen was aware of this report at the time he first used the term. Moreover, not only does Cook’s 1894 usage not capture the philosophy embodied in Jorgensen’s definition, but, looking at it now, it sadly prescribes the methodology that is responsible for the spread of DED and Emerald Ash Borer. Cook writes “urban forestry, an art requiring special knowledge, cultivated taste, and a natural sympathy for plant life… Good taste demands the observance of two rules as essential in street tree planting. First, that but one variety of tree shall be planted upon a street, and second, that the trees shall be planted at uniform distances.”

[2] Jorgensen, E. 1967. Urban forestry: Some problems and proposals. Toronto: Faculty of Forestry, University of Toronto.

[3] See also:

[4] Soil Volume Minimum for Street Trees Established in Oakville, ON (

[5] For further reading on soil volumes, see Soil Volume Minimums for Street Trees Organized by State/Province: and “Our Recommended Soil Volume for Urban Trees”:

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