Soil Volume Minimums for Street Trees Organized by State/Province

Longtime readers of this blog will know that we keep an ongoing list of all the places we know of that have implement minimum soil volumes for trees. Over the years, as the list has grown, it has also become harder to parse. Should we be organizing it by state/province, city, or the soil volume minimum itself? How can we make this information most useful and applicable outside of the areas where it has already been accepted?

It’s handy to be able to organize the information by the different criteria we collected (location, actual soil minimum, original document, etc.), which is why I used the same information to create a sortable chart.

State/ProvinceCitySoil Volume MinimumOfficial documentNotes
AlbertaCalgaryResidential Street Design Policy
AlbertaEdmontonLarge tree: 17 m3 for a single tree, or 20 m3 if shared between two treesDesign and Construction LandscapingThese are recommendations, not requirements.
British Columbia-6m3 (212 ft3) soil per tree, “and more is better”7th Edition BC Landscape Standard
British ColumbiaCoquitlamCitywide Official Plan
British ColumbiaKelownaSchedule 4 Design Drawings
British ColumbiaLangleyTownship of Langley Subdivision and Development Servicing Bylaw
British ColumbiaSurreyCity Center Design Standards
British ColumbiaVancouverSouth East False Creek Public Realm Enrichment Guidelines (search for "soil cells")
CaliforniaEmeryvilleLarge tree: 1200 ft3
Medium tree: 900 ft3
Small tree: 600 ft3
Emeryville, California Water Efficient Landscape Ordinance
ColoradoAspen and Pitkin CountyLarge (> 50’ height or spread): 2,250 ft3
Medium (< 50’ height or spread): 1,000 ft3
Small (shorter than 30’): 250 ft3
Soil area based on mature tree size, 30” deep or greater
ColoradoDenver750 ft3 of soil per treeDenver Parks and Recreation Forestry DepartmentThe city'’s “Street Tree Plan Review Checklist” states what is required on landscape plans so that the city can make a determination if there could more soil volume dedicated to the planting area. They have also recently worked with Public Works to eliminate the standard tree grate requirement. The checklist states that “5’ x 5’ pit areas shall no longer be accepted. Trenches, root paths, break out zones, structural cells, or other un-compacted soil technology are recommended.
Florida-Large (> 50’ height or spread): 2,700 ft3
Medium (< 50’ height or spread): 1,200 ft3
Small (shorter than 30’): 300 ft3
University of Florida (IFAS Extension)The project created an Urban Design for a Wind Resistant Urban Forest. Planners increased the soil and depth requirements to allow trees to mature and live longer.
GeorgiaAthens-Clark CountyLarge Canopy: 800 ft3
Medium Canopy: 450 ft3
Small Canopy: 200 ft3
Athens-Clarke County, Georgia
GuelphOntarioMedium trees:
36 m3
Large trees: 50 m3
Streetscape Manual
IllinoisChicagoParkway trees must have a minimum depth of three feet of soil. Planting areas require a minimum of 24 square feet of surface area with no dimension less than three feet.Chicago Landscape Ordinance
ManitobaWinnipegWinnipeg Street Tree Principals and Guidelines
MarylandBaltimoreAt least 1,500 cubic feet of soil for tree pits using structural soils or suspended pavement for any new impervious surfaces or retrofit and redevelopment projects.Baltimore Waterfront Healthy Harbor InitiativeThis initiative sets an example for increasing the tree canopy as a way to preserve the environment and filter 50 percent of stormwater runoff.
Minnesota-500 ft3 of soil per treeState of Minnesota Sustainable Building Guidelines (MSBG)If soil volumes cannot be met they recommend that trees be planted in minimum 8' wide by approximately 3' deep trenches so that soil volumes are shared between trees.
NevadaRenoTBD: for trees in parking lotsTBD: for trees in parking lotsTBD: for trees in parking lots
North CarolinaCharlotte550 ft3 of soil per treeStandards Manual, North CarolinaThe minimum width of the planting area is 8'’ at the trunk of the tree.
North CarolinaDurhamLarge tree: 700 ft3
Medium tree: 500 ft3
Small tree: 300 ft3
Landscape Manual
North CarolinaRaleigh600 ft3 of soil per treeStreet Design Manual (section 6.18, pages 82-86)Applies to all trees planted in the right of way for new developments. Also specifies that soil volumes should be connected between trees whenever possible.
OhioClevelandLarge tree: 1000 ft3
Medium tree: 600 ft3
Small tree: 300 ft3
Cleveland Species Planting Guide(Recommended) "Minimum soil volumes for root space are suggested to be 1–2 ft3 for each square foot of projected mature crown (Lindsey and Bassuk 1991). Other formulas have derived minimum soil volumes based on trunk to crown diameter (Urban 2008). Urban foresters generally adhere to the following soil volume minimums: 300 cubic feet for small trees, 600 cubic feet for medium trees, and 1,000 cubic feet for large trees."
OhioColumbusMinimum of 1000 ft3 (28 m3) of soil for a single treeCity of Columbus Downtown Streetscape Standards"A large root zone for trees is critical to creating a healthy tree
canopy in Downtown Columbus. In all streetscape projects,
maximizing the size of continuous soil volume should be a
priority."
OntarioGuelphLarge tree: 50 m3
Medium tree: 18 m3 (shared or shared)
Design GuidelinesApplies 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)
OntarioHamiltonIndividually planted trees in new sidewalk installations should include 21m3 of soil per tree and a grouping of 2 or more trees in a soil bed shall include 16m3 of soil per tree.Tree Preservation and Sustainability Policy Document, bylaw 15-125
OntarioMarkhamLarge tree: 30 m3 (1,059 ft3), if single, or 15 m3 (530 ft 3) if shared
Medium tree: 23m3 (812 ft3)
Small tree: 15 m3 (530 ft3)
Markham, Ontario “Trees for Tomorrow: Streetscape Manual”Minimum soil volume for tree planting in a parking lot island is 15 m3 (530 cubic feet).
OntarioKitchenerSmall 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
Urban Forest Details – Tree Planting & Establishment Best Management Practices (Appendix C of Development Manual)
OntarioOakville30m3 (1,059 ft3) of soil per tree, or 15 m3 (530 ft3) if in a shared planting trenchNorth Oakville Urban Forest
Strategic Management Plan
OntarioTorontoMinimum of 20m3 (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 planterGreen Development StandardThis is the most ambitious street tree standard we have seen yet!
OntarioYork RegionThe new Sustainability Matrix is proposing 30m3 of soil per treeSustainability Matrix
OregonTigard400 to 1,000 ft3 of soil per tree depending on the width of the right of wayUrban Forestry Manual (section 12 and Appendices 11 through 15)Applies to trees planted in streets and parking lots.
VirginiaAlexandria450 ft3 per treeLandscape GuidelinesRecommends one tree for every ten spaces in parking areas.
VirginiaTysons400 to 700 ft3 per treeStreetscape DetailsSuggested volume of 700 cubic feet and a minimum of 400 cubic feet that is allowable (pages 59 to 62).
Washington DC-Large tree: 1,500 ft3
Medium tree: 1,000 ft3
Small tree: 600 ft3
Green Infrastructure Design StandardsApplies to streets in the public right of way. See section 47.7.
West Virginia-Large tree: 970 ft3
Medium tree: 750 ft3
Small tree: 500 ft3
West Virginia Department of Environmental Protection (recommended)Municipal handbook to manage wet weather using green infrastructure.

Right now, this list only contains cities in North America – there are no soil volumes for trees that we know of in the United Kingdom – though we hope that will change.

So, same info displayed a few different ways. This post is where I will be updating information about these policies going forward, so please don’t use the old posts (from 2012) for current details. As always, if I’ve missed any soil volume minimums here, please email me at rethinktrees@deeproot.com so that I can add them.

Top image of street trees in Charlotte, NC, that were planted in 750 cubic feet of soil in 1985. Flickr credit: Fotomoe.

12 comments

  1. This is not research based information. It is people who copied other peoples work who go it from Cornell irrigation work. In other words the soil volume info only applies to Cornell and other similar places that do not irrigate trees

    • Hi John, I’m not sure I understand your comment. Which information is not research-based? This is simply a list of all the places that we’re aware of that have implemented soil volume minimums for street trees (defined as trees in the public right of way). Are you saying that tree growth/health is not tied to their access to lightly compacted quality soil?

  2. Here in Wales, at Wrexham County Borough Council, i have managed to put in place a Local Planning Policy which states “Where tree planting is proposed within hard surfaced areas (e.g. parking areas and footpaths) the size of the planting pits should be sufficient to provide an adequate volume of soil to support the eventual size of the the planted tree(s)”. Unfortunately, when this policy was adopted i didn’t have sufficient knowledge to stipulate volumes that we would require, however ever since i have been asking for a minimum of 25 metres cubed of good quality planting soil for large growing trees, 15 for medium sized trees and 8 metres cubed for small growing trees, with these figures being reduced by a third for shared pits. When we come to revise our local planning note on trees & development, i will be putting in these requirments.

    With regards to CU soil i have been asking for four times the above sizes, as CU soil contains 80% stone therefore the rooting volumes jhave to increase in order to provide the same amount of soil.

    Its amazing the number of landscape architects and developers that have been actively fighting this policy as they do not want to spend money. Traditionally in Britain, the vast majority of developers have viewed landscaping as something that municipal planning forces on them and they spend as little on the hole as they try to do with the trees to be planted. The old adage of spend a £100 on the hole and £10 on the tree seems to have been forgotten by so many in this industry. Its such a shame that a huge percentage of the landscape architects over here in Britian do not keep up with continual professional development and still believe that a large tree will survive in a hole with 1 metre cubed of soil. In the past here, a large number of trees were planted in concrete rings in hard surfaced areas, which you would be lucky to get 0.5 metres cubed of soil in, these are what i call concrete tree coffins, and any tree planted in a hard surfaced area which does not provide sufficient volume of soil is a tree coffin.

    The lack of understanding of the basic requirements of trees i.e sufficient rooting volume of decent soil by a hell of a lot of landscape architects over here in Blighty is so depressing. Thus having minimum rooting volume policies is such a good idea. I applaud Deeproot for highlighting who actually has policy on rooting volumes for trees. Lets hope more get this type of policy adopted in their municipalities.

    • Moray, thank you so much for commenting. It’s a slog trying to educate and get everyone on the same page about this fundamental truth: trees need soil. Even if you weren’t able to specify a soil volume minimum in Wrexham the first time around, you’ve laid some important groundwork for future changes. Hopefully those will happen yet! Thanks for everything you’re doing for trees.

  3. I’m not sure that West Virginia should be included in the list. The EPA guidebook listed on their website is just that – a resource for people interested in reading it. To my knowledge, West Virginia has not truly embraced any recommended minimum soil volume requirements.

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