When the Watershed Conservation Center in Ontario, Canada was built in 2012, a 75 m2 (807 sf) live roof garden was installed on either side of the sidewalk leading up to the front doors. The live roof sits on top of part of the basement of the old office building, which was retained and renovated into a storage room.
The live roof is a component of the LEED designation that the building received and one of the requirements to achieve this designation is to limit the area of paved surfaces that contribute to runoff and the urban heat island effect. Live roofs are designed to absorb and retain rainwater for several hours, thus reducing peak runoff by as much as 30-50%. The green plants absorb the heat and provide cooler, moister air to the nearby concrete environment.
The roof was installed in modules that contain about 3 inches (8 cm) of engineered growing medium (crushed stone), which supports a mix of low sedums and chives. The plants are selected for their ability to grow in these unique conditions. The sedums are drought tolerant, so do not need watering except in extreme droughts. During the summer flowering season, the flowers attract pollinators, especially bees.
Maintaining a live roof does require some effort and trouble shooting. Soil tests are carried out every other year and a low phosphorus fertilizer is added as needed. Ongoing weeding is important to keep the sedums and chives the dominant plants.
From time to time, plant dieback is noticed in various spots. This is remedied by clipping the top 1-2 inches of healthy sedum plants, and laying the clippings on the bare soil. They root where they touch the ground and continue growing and spreading.
The life expectancy of the live roof soil medium is 60-70 years. They are pleased with the performance and beauty of their live roof. Long live the live roof!
You can read the original article at thamesriver.on.ca
Can living roofs have vegetable gardens on them?
They could have vegetable gardens, as long as there is sufficient soil and the owner is willing to make sure it is taken care of appropriately.