Published by City Farmer, Canada's Office of Urban Agriculture


Urban Agriculture:
The Potential of Rooftop Gardening

Chapter 4: Conclusion

By Joseph St. Lawrence
Joseph St.Lawrence

Report of a Major Project submitted to the Faculty of Environmental Studies in partial fulfilment of the requirements for the degree of Master in Environmental Studies.

York University, North York, Ontario, Canada.
July 29, 1996 [Images are not included here.]

Chapter 2 (The Site and the Plan)
Chapter 3 (Observations)
Chapter 4 (Conclusion), and References


When I began this project, I had visions of covering the city's vacant roofs with productive verdure -- standing on the Field to Table rooftop and surveying the surrounding empty roofscape, I felt like the first pioneer to reach the prairie. I now realise that this is an impractical idea. There are too many technical barriers to make gardening a convenient and inexpensive undertaking on most roofs. Rooftop gardening is not without its benefits however, and I believe that it has the potential to serve local needs in many circumstances. Summarised below are some of the positive and negative aspects (pros and cons) of rooftop cultivation illuminated by this project.



Perhaps one of the greatest benefits of rooftop gardens is their nearness. An individual or business cultivating their roof space does not have to make the trip to and from an allotment or community garden. As Hough (1995) observes, community gardens are not often found where they are most needed. Gardens on community centre roofs, for example, could help address this dislocation to some degree.


One of the great insecurities of urban agriculture centres around tenure. Community gardens, allotments, and temporary garden plots are often displaced by what are viewed as more productive uses of the land. Lack of tenure has a profound affect on the activities undertaken in an agricultural enterprise. Many of the improvements sites require are labour intensive, and gardeners will be reluctant to invest the time and energy required if they cannot be assured continued use of the land. Rooftop gardens are not likely to face competition with other uses of the space, and can therefore offer greater security of tenure than other spaces.


A rooftop, by mere virtue of its nature, has limited accessibility. The Field to Table warehouse is in one of the more neglected areas of Toronto, and theft and vandalism would very likely have been a problem at ground level. Security from animal pests is also an issue. There is a pair of groundhogs resident in the overgrown area adjacent to the warehouse, and keeping them from devouring my crops would have posed a serious challenge. Racoons are other common garden marauders found in the city. I enjoyed freedom from all of these problems because of the garden's elevation.

Water and light

Gardens built in undeveloped parts of the city may have trouble accessing water. Roofs, in contrast, are almost always in close proximity to a municipal water supply outlet. They have the added bonus of providing an opportunity to collect rain water from the roof -- an option which should be explored, as I believe that harvesting rain water is more appropriate than the use of potable water for crop production.

Roofs do not fall in the shadow of the buildings they cover, and so often enjoy the best exposure to sunlight on a given lot. On the Field to Table property there are only a few small spaces not cast in the shadow of either trees or the warehouse for significant portions of the day. In this respect, the rooftop is the best location for a garden on the property.



Unfortunately, most roofs in Toronto are not designed to support gardens year-round. The considerable labour involved with moving soil would have to be repeated in spring and fall each year. This process would also make it impossible to develop a stable soil ecosystem and difficult to cultivate perennials. Clearly, for a rooftop garden to be an appropriate use of space, the roof must be able to support the weight of the garden throughout the year.


Accessibility is another important issue. As mentioned earlier, I believe that much of the educational and social potential of my garden was lost because it is difficult to get to the site.

Safety is another factor: both for the gardeners and for those on the ground. If a rooftop is to be used as a public space, it must have a 3'6" railing, according to the Toronto Building Code. This could be an expensive undertaking on a large roof, and might necessarily limit the amount of space available for cultivation.

The Ideal?

Although there are difficulties associated with using rooftops for urban agriculture, they do have some potential. Ideally, restaurants, or catering companies could use their own roof spaces to provide rare or expensive ingredients for their kitchens. The labour required would not be great, and could easily be performed by those already employed at the site.

There is an opportunity to cultivate markets in the city for products that are delicate, or perish too quickly to be shipped in from elsewhere (edible flowers for example). But I no longer believe that the economic returns possible from the use of rooftop gardens would make growing these products economically sustainable on most city roofs. There is simply too much labour required to generate an adequate return from the sale of produce. The main problem is that an extensive planting, although capable of generating a decent income, would require a colossal amount of labour in spring and fall to move soil to and from the roof. Strong rooftops would of course not require this effort, and therefore have the most potential for generating an economic return.

My experience during the project summer has led me to believe that rooftop gardening is unlikely to thrive unless it meets many needs in its environment. Economically, the activity could cover costs and perhaps make a small profit, but the returns on labour would probably be too small to make it worthwhile from this standpoint alone. If, however, the garden can serve other goals while generating income on the side, then it could indeed be a worthwhile endeavour. The activities of an organisation like Field to Table, for example, can be augmented through the use of a rooftop garden. It is an ideal spot to carry-out the gardening component of the Focus on Food programme. By using it as a classroom, the costs of labour for growing produce would be eliminated. The income produced by this and related value-added activities (e.g. making preserves, herb condiments, or salad mix) could provide revenues to improve the programme while meeting the programme's needs for produce and garden training facilities.

I was very fortunate to have the opportunity to do this project at the Field to Table warehouse. The vibrant community there and the organisation's interest in food security were instrumental in illuminating the potential of rooftop gardening. Although the activity is not without its problems and limitations, it could effectively meet some community needs in an appropriate environment. It is not likely to have a substantial impact on urban food production however, and I would suggest that efforts in this regard focus on promoting the use of other unused spaces in the city.


Chapter 2 (The Site and the Plan)
Chapter 3 (Observations)
Chapter 4 (Conclusion), and References

pointer Return to Contents' Page pointer

Revised February 24, 1997

Published by City Farmer
Canada's Office of Urban Agriculture