Project Statement

Through urbanization, what was green becomes grey. Given the abundance of pavement in cities, it is argued that plants such as spontaneous vegetation should be better integrated into streets and sidewalks. To develop such pavement designs, I wandered over 420 km through cities in Southern Ontario, photographing spontaneous pavement vegetation for design inspiration. Photos were then classified and referenced with city standard drawings to develop pavement designs. The 11 designs generated have potential to provide ecosystem services such as improved stormwater management and pollinator patch connectivity between larger green spaces. Moreover, they show that grey spaces can offer moments of beauty and joy, helping grey to be green again.

Project Narrative

Paved surfaces dominate the urban landscape, reducing green space. This has implications for ecological and hydrological systems, and access to nature in cities. Cadenasso and Picket (2008) noted that efforts to increase biodiversity in cities are often limited to parks and other reserves, and that plants should be better integrated into urban grey space. Investigating sidewalks and the overlooked presence of spontaneous pavement vegetation (SPV), Bonthoux et al. (2019a) found that these areas are quite biodiverse. They concluded that, given the potential ecological services, designers should develop pavement designs that better integrate SPV. A later study by Bonthoux et al. (2019b) evaluated people’s preferences for vegetation on sidewalks; they found that pavement with SPV were perceived as “less kept, but more beautiful and less boring”.

Responding to this literature, my research goal was to identify opportunities to leverage the potential of SPV in standard pavement design. Additionally, the relationship between pavement characteristics and the presence of SPV was investigated to understand these growing conditions. This also gave insight into the character of cities, and how SPV fits within the vegetation context of urban areas.

Preliminary research methods involved wandering through cities in Southern Ontario, Canada, photographing and observing spontaneous pavement vegetation for design inspiration. Field-work photographs were then analyzed and categorized to identify design opportunities and develop design ideas.

In total, I walked and bicycled over 420km, took over 2700 useable photos, classified 16 photo categories, and developed 11 design ideas. These designs are subtle as they use the joint margins in design standards for planting space. By widening these margins slightly and filling with a growing medium, desirable plant growth could be supported; resulting designs could be considered as linear vegetative strips, or micro-boulevards.

These small design interventions have the potential to make a big impact. Through integrating plants in paved areas between large green spaces, biodiversity and ecological connectivity can be improved in cities. This, along with the adaptiveness and drought tolerance of SPV, could help improve the resilience of urban areas in a changing climate. By increasing the permeability of paved areas, stormwater management could be improved; this is especially important as the frequency of high rainfall events increases. Additionally, by integrating plants into everyday spaces, greater access and incidental interactions with nature can be created, improving mental health and a sense of well-being.  

There is little existing research with which to compare these results; however, future research can explore implementation and evaluation of these designs. This includes identifying best species for planting design, developing construction ideas further, investigating temperature and moisture regimes in pavement margins, measuring hydrologic impact, developing growing media, evaluating design performance, and assessing aesthetic preferences.

In existing grey areas, it is recommended that SPV be left alone so that ecological contributions are retained. In future construction projects, designers could apply these results to test their merits. In designers’ efforts to improve human/nature interactions and respond to stormwater management, small moments can add up through re-imagining pavement planting design.