For : Thursday November 25, 2004
Everyone: I’ve been quite busy this week with 4 th year related stuff, so I only had a bit of time to search about green roof vegetation. I did find a few interesting links, and I have included them below. I also e-mailed several professors in the region (nearby US) who research green roof plant selection and diversity, so hopefully they can provide more info.
Later,
Jacqueline
Example #1 http://www.cmhc-schl.gc.ca/en/imquaf/himu/buin_020.cfm
Toronto Ontario
Summary: This particular case study, involves a high budget green roof, therefore the plants listed fit the climate of waterloo, but may be out of the scope of our project. More research about the plants and cost will have to be performed.
The roof is landscaped with a prairie meadow growing in two green roof plots. The green roof proper is approximately 10,000 square feet and is surrounded by an additional 15,000 square feet of hard surface concrete pavers. The decision to install the green roof was made by the development in the final phases of the redevelopment project in order to maximize the area available for planting without needing to adjust the structural loading capacity of the building.
The total redesign and regeneration of this 1,070,000-square-foot complex is believed to be the largest of its kind in North America.
Highlights
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Building Type: 12-storey, multi-use condominium complex
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Units: 504
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Typical Population: 500-800
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Location: 155 Dalhousie Street Toronto, Ontario
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Status: Renovations/conversion of complex completed in February 2000
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Cost of green roof retrofit: $200,000
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Area of green roof: 10,000 square feet of planting area 15,000 square feet of decorative concrete pavers
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Green roof type: Extensive
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Saturated weight: >30 lbs per cubic foot
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Developer: Cresford Development Inc.
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Architect: Paul Northgrave Northgrave Architect Inc.
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Landscape Architect: David Lieberman, David Lieberman Architects Terry McGlade,
Perennial Gardens
Plant Selection
The primary issue when selecting the plants and designing the green roof plan, was the excessive wind and sun exposure. The green roof is located on the roof of the twelfth storey and

has southern exposure. Native species, such as grasses, that function well in extreme conditions were selected. The plants were also grown in 'plug' sizes that ensured firm roots in the shallow growing medium.
37 different species of native Ontario plants were included in the design. Examples of the selected species are: Switch Grass (Panicum Virgatum), Hairy Beardtongue (Penstemon hirsutus), Gray-headed Coneflower (Ratibida pinnata), Pale Purple Coneflower (Echinacea palida), Woodland Sunflower (Helianthus divaricatus), and Sedum (spurium red, Ewersii, sexangulare, kamtachaticum, spurium Album). The total budget for the plants was $67,000, which included their transport to the site and installation.
Example 2 http://www.city.waterloo.on.ca/pws/environment/Topical/GreenRoof/GRproc.pdf
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Listing of a lot of specific plants, trees and shrubs (grouped by whether extensive or intensive)
Example 3 http://www.c2p2online.com/documents/GreenRoofsComplete.pdf
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Work report on green roofs in Ontario for Canadian Centre for Pollution
Prevention
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Discussion of types of plant selection
Example #4 http://www.ecoroofsystems.com/construct_files/c_construct.html
The selection of drainage medium, depth and type of soil and selection of plant specimens should be carefully chosen based upon local varieties of plant species and local climatic conditions.
Soil Substrate- The growing medium or soil substrate can be selected from several engineered mixes designed by various suppliers. By using a mixture of native soil upgraded with organic or mineral additives (peat, humus, wood chips, sand. lava or expanded clay) it is possible to achieve optimum water retention, permeability, density and erosion control necessary to support the green roof vegetation. The thinner the soil layer, the higher the physical demands on the plants. Some problems in the past have been the result of too shallow soil depths, resulting in root damage from heat and frost fluctuations. The soil must be deep enough to protect the roots from frost and heat damage.

Plant Material- The vegetation layer is the most vital and exciting part of the green roof, and as such suitable and dependable plant material selection needs to be assessed on a region basis. Characteristics of landscaping typically used in extensive green roof systems include shallow root systems, regenerative qualities and resistance to direct radiation, drought, frost and wind. A much larger variety of plant selections are available for intensive roofscapes due to the opportunities offered by greater soil depths.
Compatibility issues of green roof type, anticipated use, temperature, humidity, rainfall and sun/shade exposure are important elements for successful plantings of any kind.
Native and culturally adaptable plants used for the artificial environment of a green roof need to be reviewed for heat and drought tolerance. This is extremely important since most systems are designed to be low maintenance. The plant make-up is customized to meet the specific function, environmental conditions, climate zones and aesthetic requirements of the individual application. The soil material is lightweight, long lasting and absorbent, able to retain water to nourish the plant life. The plant materials usually require supplemental irrigation and fertilization while getting established during the first year. Due to the return of organic matter to the soil additional fertilization is not usually necessary.
The desired seasonal visual impact of a green roof may also dictate the plant material.
The summer/ winter vegetative aspect changes just like it would in any landscape. What happens to the green roof plants in the dormant season? Depending on the ratio of herbaceous to evergreen plants selected, the roofscape can have varying colors, heights and textures to create winter interest.
Plant Material Application and Maintenance
Plant material can be applied to green roofs by several means: pre-vegetated mats or blankets; direct on-site planting of sedum cuttings and/or seed or root plants; hydroplanting; or any combination of these methods. The types of plantings selected dictate their planting times. Root plants can be planted throughout the entire growing period if they are sufficiently watered. Plants used for extensive landscaping are cultivated in special flat-bottomed planting trays. The sowing of sedum cuttings and/or seeds is restricted to spring and autumn. Simple extensive green roofs should not require any regular maintenance after the first two years.