Chapter 11. Hard Surface Planting

Hard Surface Planting

One of the most persistent challenges in urban forestry is the ongoing battle between tree roots and pavement. Trees planted close to hard surfaces such as pavement, asphalt, or concrete, often suffer from soil volume restriction and limited access to nutrients, which can lead to root damage, root girdling, and pavement lifting, and cause roots to grow in less favourable areas (Mullaney, Lucke, & Trueman, 2015a). These impacts can create safety hazards for street users, cause concern for property owners and residents, and impact the aesthetic properties of the urban forest. Management practices include planting appropriate tree species, installing covers or grates over planting pits that accommodate tree growth, planting ground covers around tree trunks to reduce foot traffic and compaction, using an appropriate soil medium to encourage deep tree root growth, constructing continuous channels that connect individual planting pits, implementing pervious paving around trees, and planning for and providing adequate irrigation. A variety of methods have been developed and implemented to increase tree survival in hard surfaces by using the best possible planting method for a given site.

Canadian online resources:

• City of Toronto: Presentation on the Tree Planting Solutions in Hard Boulevard Surfaces Best Practices Manual (PDF)
• GreenBlue Urban

Non-Canadian online resources:

• American Society of Landscape Architects: Structural Soils: A New Medium to Allow Urban Trees to Grow in Pavement
• Cornell University, Urban Horticulture Institute: Structural Soils
• Cornell University: CU Structural Soil^© (PDF)
• Deep Root Products
• Herold, Koeln, & Cunningham: Mapping Impervious Surfaces and Forest Canopy Using Classification and Regression Tree (Cart) Analysis (PDF)
• London Tree Officers Association (UK): Surface materials around trees in hard landscapes
• Virginia Polytechnic University: Trees for Parking Lots and Paved Areas (PDF)
• Woods Hole Research Center and the University of Maryland: Using IKONOS Imagery to Assess Impervious Surface Area, Riparian Buffers and Stream Health in the Mid-Atlantic Region (PDF)

Further reading:

Booth, D. B., Hartley, D., & Jackson, R. (2003). Forest Cover, Impervious Surface Area and the Mitigation of Urbanization Impacts. Journal of the American Water Resources Association 38(3), 835-845.  http://dx.doi.org/10.1111/j.1752-1688.2002.tb01000.x

Mullaney, J. Lucke, T., & Trueman, S. J. (2015a). A review of benefits and challenges in growing street trees in paved urban environments. Landscape and Urban Planning, 134, 157-166. https://doi.org/10.1016/j.landurbplan.2014.10.013

Mullaney, J. Lucke, T., & Trueman, S. J. (2015b). The effect of permeable pavements with an underlying base layer on the growth and nutrient status of urban trees. Urban Forestry & Urban Greening, 14(1), 19-29. https://doi.org/10.1016/j.ufug.2014.11.007

de la Mota Daniel, F. J., Day, S. D., Owen, J. S., Stewart, R. D., Steele, M. K., & Sridhar, V. (2018). Porous-permeable pavements promote growth and establishment and modify root depth distribution of Platanus × acerifolia (Aiton) Willd. in simulated urban tree pits. Urban Forestry & Urban Greening, 33, 27-36. https://doi.org/10.1016/j.ufug.2018.05.003