The Sweet Willow Community Garden sits on top of a steam heating plant that services 200 LeBreton Flats homes.
McCallum says that the small rooftop garden extends the growing season by up to four months depending on the weather.
The garden is one of 26 urban community gardens incorporated by the strictly organic Ottawa Community Gardens Network.
Ten lucky gardeners tend to plots about eight by four feet, with moe than 25 on a waiting list to scoop up a spot. But getting a space at Sweet Willow takes up to three years.