Since its installation in 2000, the Green Roof Infrastructure Demonstration Project at Toronto City Hall is thriving.

The demonstration site is located on the podium roof at Toronto City Hall and is fully accessible to the public between the hours of 9 a.m. and 5 p.m. from the front security desk on the main floor. Below are descriptions of the eight green roof plots, each of which represents different green roof applications.

Extensive Plots: Extensive green roofs are characterized by their low weight, low capital cost and minimal maintenance. They are typically non-accessible to the public and have the largest potential market application. Plants on extensive green roofs are usually low and hardy, typically alpine, dryland or indigenous. Plants such as sedum, thrift, armeria and phlox are located in the demonstration project’s two extensive plots.

Semi-Extensive Plots: Semi-extensive green roofs have a combination of extensive and intensive qualities. Intensive green roofs are characterized by greater weight, higher capital costs, more diverse plantings and higher maintenance requirements. The two semi-extensive plots require greater loading capacity than extensive plots but they can accommodate a much wider plant selection due to increased soil/growing media depth. They provide greater energy efficiency and stormwater retention and are often accessible. Plants featured on the City Hall plots include iris, day lilies, echinacea purple coneflower, coreopsis and penstemon.

Black Oak Savannah: The Black Oak Savannah ecosystem is a native prairie ecosystem that is now endangered in North America. This plot provides an opportunity to protect and encourage biodiversity. The plants in this plot are drawn from the High Park gene pool and include big blue stem, heath aster, little blue stem and greenheaded cone flower.

Bird & Butterfly: The bird and butterfly garden is designed to attract a wide variety of birds and butterflies and is a unique opportunity to create new habitat in an urban centre. The species in these plots are Western Ontario natives from High Park in Toronto, Sheridan Nurseries and Sweet Grass Gardens. They include eastern columbine, bottlebrush grass, grey headed coneflower, New Jersey tea, and winecup.

Kitchen Garden/ Permaculture: The two urban agriculture green roof plots at City Hall demonstrate the potential of rooftop farming to provide high quality produce within the city. One plot features perennials and vegetables such as peppers, tomatoes, sage and chives. The other plot applies some of the principles of permaculture. It contains a space-efficient spiral herb garden and utilizes keyhole pathways, which provide improved access for tending to the plants. The plot also contains the 3 Sisters Native American planting – corn, beans and squash. In this arrangement, the beans fix nitrogen for the squash and the corn is a trellis for the beans. Toronto’s Field to Table has been helping to develop these plots and will be marketing the produce in Toronto.

For more information about the Demonstration Project, please visit the site and pick up a ‘self-guided tour’ brochure at the security desk on the main level of City Hall.