DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Acknowledgements: Prepared by: Scott Torrance, Brad Bass, Scott MacIvor and Terry McGlade in conjunction with Toronto City Planning Division Illustrations: Grace Yang, Scott Torrance Landscape Architect Inc. Photographs: See individual photographs Design and Layout: Graphics and Visualization, Urban Design, Toronto City Planning Divison www.toronto.ca/greenroofs
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Table of Contents 1.0 Introduction and Background 5 2.0 Natural Heritage and Biodiversity Objectives 6 3.0
Opportunities and Constraints 3.1 Extensive and Intensive 3.2 Roof Types 3.3 Native Vs Non Native 3.4 Invasive Species
8 8 10 10 10
4.0 Design Guidelines 4.1 Design Factors 4.1.1 Depth, Topography and Composition of Growing Media 4.1.2 Vegetation Diversity 4.1.3 Structures 4.2 Design Strategies 4.2.1 Increase Depth of Growing Media 4.2.2 Vary Composition (Structure) of Growing Media 4.2.3 Provide Topographic Variety 4.2.4 Provide Microclimates 4.2.5 Diversify Plant Species 4.2.6 Provide Perching Habitat 4.2.7 Provide Nesting Opportunities 4.2.8 Provide Water Source(s) 4.3 Design Analogues 4.3.1 Recreate Native Landscapes 4.3.2 Design to Attract Specific Fauna 4.3.3 Design to Support Adjacent Ecosystems
11 11 11 11 12 13 13 13 13 14 14 14 15 15 16 16 19 22
Sources/Resources Appendix A: Recommended Plant Species Appendix B: Plant Species to Avoid Appendic C: Plants used by Butterflies and Caterpillers
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
1.0 Introduction and Background Green roofs have many environmental benefits. They help reduce the effects of the urban heat island and associated energy use, manage stormwater runoff (reducing the pollutants that enter our waterways), improve air quality and beautify our city. Green roofs also provide an opportunity to create habitat and enhance biodiversity in the urban fabric of the City. The City of Toronto has a bylaw to require the construction of green roofs on most types of new building development. The City also encourages green roofs through the Eco-Roof incentive program and by providing explanatory tools and resources through the City’s green roof website. All green roofs in Toronto, including those required by the Green Roof Bylaw, are required to meet minimum standards which are defined in the Toronto Green Roof
Construction Standard. Additional guidance for green roof construction is found in the Toronto Green Roof Construction Standard Supplementary Guidelines. These Guidelines for Biodiverse Green Roofs identify, describe and illustrate best practices for creating habitat and promoting biodiversity on green roofs in Toronto. They are intended to support and expand the Toronto Green Roof Construction Standard Supplementary Guidelines. These guidelines are primarily designed for use by architects and landscape architects involved in designing green roofs but they may also be of interest to others who wish to understand how green roofs can be designed to enhance and support biodiversity.
About the Green Roof Bylaw Toronto is the first City in North America to have a bylaw to require and govern the construction of green roofs on new development. Toronto Municipal Code Chapter 492 Green Roof came into effect on February 1, 2010 and applies to most building permit applications for new development that are over 2,000m2 in gross floor area. The Bylaw requires that new development include a green roof covering between 20 and 60 percent of the roof area depending on the size of the building. Toronto Green Roof Construction Standard Supplementary Guidelines The Toronto Green Roof Construction Standard Supplementary Guidelines provide designers and others with best practices, explanatory material and other green roof resources. The Supplementary Guidelines contain the following best practices which provide impetus to design to promote biodiversity:
• Growth media depth over 100 mm is encouraged. Vegetation should be: • As defined in ASTM E2400 - 06 Standard Guide for Selection, Installation, and Maintenance of Plants for Green Roof Systems • Native or adaptive from the Southern Ontario area • Appropriate for the Toronto climate and building exposure • Drought resistant to minimize the need for irrigation • Non-monoculture TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
2.0 Natural Heritage and Biodiversity Objectives The City of Toronto Official Plan recognizes the importance of protecting, restoring and enhancing the health and integrity of the natural ecosystem and supporting biodiversity. These Guidelines help to implement policies in the Official Plan which seek to support this policy objective. Toronto Official Plan Policy 3.4.1 “To support strong communities, a competitive economy and a high quality of life, public and private city-building activities and changes to the built environment, including public works, will be environmentally friendly, based on: b) Protecting, restoring and enhancing the health and integrity of the natural ecosystem, supporting bio-diversity in the City and targeting ecological improvements” Green roofs have the potential to enhance biodiversity in urban areas. In the City of Toronto, green roofs have the potential to contribute a significant area of habitat to the urban matrix. A 2005 Report on the Environmental Benefits and Costs of Green Roof Technology for the City of Toronto estimated that 21 percent of the total land area in the City is covered with roof and that 8 percent, or approximately 5,000 hectares of City’s land area, is covered with roof that could be suitable for green roof. The study concluded that if these areas were converted to green roof they would provide opportunities to recreate some of the habitat and restore some of the biodiversity that has been lost due to urbanization.
Example of hybrid meadow/grassland community. Two views of Robertson Building, 215 Spadina, Toronto (McGlade, 2011)
A 2010 discussion paper on Using Green Roofs to Enhance Biodiversity in the City of Toronto reviewed literature on green roofs and biodiversity and identified opportunities, locations and strategies to enhance biodiversity and support Toronto’s natural heritage system by increasing the area of habitat for flora and fauna, acting as transition zones or buffers between natural habitats and the surrounding urban area and performing ecosystem services.
Green roof adjacent to High Park, Toronto (McGlade, 2011)
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
When development is proposed in or near the natural heritage system, the Official Plan requires that the proposed development’s impact on the natural heritage system be evaluated and measures to mitigate negative impacts and restore and/or improve the natural heritage system be identified. In keeping with this policy, where a green roof is to be constructed in or abutting the natural heritage system, the Toronto Green Standard encourages applicants to “consider providing a minimum growing medium depth of 150 millimetres (6 inches) to accommodate a greater variety of plant species, to promote biodiversity”.
Toronto’s Natural Heritage System Toronto’s Natural Heritage System is an evolving mosaic of natural features and functions across the City, including forest, wetland and meadow habitats; valley and stream corridors, the shoreline of Lake Ontario and other significant natural features and is connected to natural systems outside of the City including the Greenbelt. Toronto’s natural heritage system is illustrated on Map 9 of the Official Plan and is based on a Natural Heritage Study (2001) which identified and mapped the location of natural features and functions across the City.
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Toronto Green Standard is a two-tier set of performance measures for sustainable site and building design for new private and public development. The Toronto Green Standard requires green roofs on buildings included in the City of Toronto Green Roof Bylaw and encourages green roofs on other buildings.
Extensive Green Roof, 75mm depth, sedums and chives only; Victoria Park Subway Station, Toronto (Torrance, 2009)
3.0 Opportunities and Constraints 3.1
Extensive and Intensive
Green roofs can be classified as either extensive or intensive, depending on the depth of substrate used and the level of maintenance required. Most of the green roofs that have been constructed under the Toronto’s Green Roof Bylaw are extensive green roofs. Extensive green roofs generally have shallow, well drained substrates and hot dry conditions that are generally only suitable for a few drought tolerant species and minimal biodiversity. Intensive green roofs have deeper substrates that can support a greater variety of habitats and biodiversity. Green roofs can also involve a combination of the two types.
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Example of hybrid meadow/grassland community, extensive green roof, 150 mm depth at Jackman Public School, Toronto (McGlade, 2011)
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Key differences between extensive and intensive green roofs Roofing Element
Growing Media/ Structural Preparation
Extensive Green Roof
Intensive Green Roof
Depth of growing media generally between 50 - 100 mm (2 – 4 inches) • Minimal to no irrigation • Light weight • Structural engineering usually not required • Suitable to cover large surface areas
Depth of growing media greater than 100 mm (4 inches) • More likely to require irrigation • Heavier in weight • Requires structural engineering • Used over smaller areas or in landscaped containers
•
•
Stressful conditions for plants requires low growing drought resistant species • Can support few plant species, generally monoculture
•
Shallow substrates subject to the effects of freezing and extreme drought. Overwintering survival is low. • Limited opportunity to incorporate habitat features • Little opportunity for habitat functions
•
•
Vegetation
•
Biodiversity Characteristics
Deeper substrate can support wider range of native plant species • Can be designed to simulate greater range of plant species and habitats
Deeper substrate depths buffer against the effects of freezing and extreme drought • opportunities to incorporate habitat features for mobile species such as birds and insects • Greater opportunity for restoration of habitat functions
Source: Using Green Roofs to Enhance Biodiversity in the City of Toronto, 2010.
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
3.2 Roof Types
3.3 Native Vs Non Native
No roof necessarily presents the optimal environment for creating a biodiverse ecosystem, but where there are constraints, there are opportunities. A rooftop is already a harsher environment than what most plants encounter on the ground - a result of higher temperatures, higher wind speeds and reduced water-holding capacity in comparison to most environments existing at ground-level. In full sun, these stresses are exacerbated, necessitating the need for regular irrigation.
There is ongoing debate about the use of native versus non-native or exotic plants. There are several arguments in favour of using native plants. Native plants are well adapted to local environmental conditions and are more likely to form self-sustaining plant communities that require less longterm maintenance, because they are already adapted to this climate and its extremes. Native plants also provide important sources of food and shelter for native birds, butterflies and other insects. Use of local vegetation in planting design may also allow colonization by other local species to occur more quickly as they are already adapted to the native vegetation.
Flat roofs that can support an intensive green roof may only be constrained by cost, sun or shade. Many flat roofs will become extensive green roofs due to limitations on the roofs weight-bearing load and/or budgetary considerations. Flat roofs do not have significant variability in water drainage and offer lower niche diversity, and thus less opportunity for different plants to exploit these novel habitats. Opportunities may exist to vary growing media topography by adding depth on those parts of the roof that can support the additional load (e.g. above structural areas). Sloped green roofs are not as common in North America as they are in Europe because more structure is required to keep the growing media in place, which in turn raises cost. However, sloped roofs may allow for (or require) a wider plant palette in comparison to a topographically homogenous extensive green roof. The upper regions of a sloped roof will drain faster than lower regions, creating niches for different plant species better adapted to drier conditions (e.g. Sedums) at the high side and wetter conditions (e.g. grasses, asters) in the low areas. Gravity, wind, and dry conditions can topple loose soil and plant material, particularly since sloped roofs often do not have a parapet for added protection. In terms of moisture, adding slope is analogous to adding depth on an increasing gradient from top to bottom. Sloped roofs may also provide areas of partial to full shade if they use shed or hip configurations. This necessitates plant species selection to withstand these varying light conditions.
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There are also several arguments in favour of using non-native plants primarily because the climate on a roof is different than on the ground. It is generally hotter and drier, and many native plants do not adapt well to this environment. There are non-native plants that are already well-adapted to growing in confined spaces, and these plants may be better suited to growing on a roof. For example Sedum varieties from alpine regions have a proven track record on green roofs and these plants can still be used as part of a green roof that is designed to provide habitat for birds and insects.
3.4 Invasive Species Certain invasive plants can colonize green roofs. These are mostly ‘hitchhikers’ in soil or plant material intentionally planted during installation but also some plants species with very mobile seeds dispersed by wind or by birds. A species which is not typically invasive may act invasive under certain conditions (e.g., Canada goldenrod and Manitoba maple). Plant colonizers require free nutrients to get established, and a high diversity of plants can be used as a strategy to minimize free nutrients, thus reducing or eliminating the ability of invasive species to colonize a green roof. Some colonizers like dandelion (Taraxacum officinale) provide considerable nectar and pollen resources for many kinds of beneficial insects, as does bird vetch (Vicia cracca) a nitrogen-fixing leguminous plants that improves accessibility of other plant species to this essential soil element.
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Aggressive invasive species such as garlic mustard and buckthorn, which are a threat to urban ecosystems. typically, these plants do not become established on green roofs due to the elevation, substrate depth and nutrient profile of green roofs. A list of recommended plant species (native and non-native) is provided in Appendix A. Plants to avoid are found in Appendix B.
4.0 Design Guidelines 4.1
Design Factors
There are three design factors that have been linked to the creation of biodiverse green roofs:
• Variation in depth, topography and composition of growing media, • Vegetation diversity, and • Structures to create niche spaces for organisms These three factors are described and illustrated below.
4.1.1 Depth, Topography and Composition of Growing Media Depth of growing media or substrate is a considerable constraint on the variety of habitats that can be created on a green roof. Roof environments are subjected to many stresses such as intense temperature and moisture changes, so shallow substrates can intensify the already extreme ecological conditions. In general, as the depth of growing media increases, the opportunity to promote biodiversity also increases, simply because a greater range of plant species and plant types can be accommodated. Installation costs (both for the vegetated assembly and the structure to support it) increase as depth of growing media increases. Maintenance and irrigation requirements may increase as well for deeper roofs.
DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
In Toronto, the diversity of plants that can survive increases dramatically when depth of growing media increases from 100mm to 150mm (4 – 6 inches). Green roof substrate depths above 100mm (4 inches) or more will help to avoid significant die-back in the winter or during hot summer months. Topographic variation in substrate depth across a green roof is also a way to increase biodiversity by creating a series of different microclimates, and subsequently microhabitats, within the same green roof zone. Thin substrate areas allow sparse vegetation to develop, whereas small hills or mounds of thick substrate support taller, denser vegetation. Depth can only be added on those parts of the roof that can support the additional load. Composition of the growing media can play a role in supporting biodiversity by varying the granule size of the substrate. Recreating native soil structure, or aggregate composition may also be considered, although little research has been completed on this subject. Gravel can also be used on bare areas on a roof to create habitat diversity however the Green Roof Bylaw restricts the use of substrate based extensive green roofs due to the requirement of 80 percent coverage and noxious weed restriction (if self-seeding is to be relied upon). One strategy would be to meet the minimum area required by the Green Roof Bylaw and achieve 80 percent coverage, while providing other non-planted areas to allow self-seeding. Removal of noxious weeds from these areas would need to be part of the ongoing maintenance plan.
4.1.2 Vegetation Diversity The vegetation layer of a green roof plays a significant role in fostering biodiversity. Maximizing the diversity of plant species and plant life forms (succulents, herbaceous perennials, woody plants, coniferous, deciduous, etc.) has many benefits, increasing the opportunities for pollination and food, shade, nesting, perching, nutrients, etc. Large roofs or roofs with high load bearing capacity provide the greatest opportunity for diversity by
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
permitting a greater range of vegetation type and size, including trees and shrubs, but extensive green roofs provide excellent opportunities to create grassland communities. The most common extensive green roofs are planted with sedums. Establishment of monoculture green roofs will generally necessitate greater maintenance and careful monitoring to ensure proper viability of the single species.
4.1.3 Structures The use of structures is a simple approach that can be used to manipulate and increase the utilization of the roof as habitat. One technique that can be integrated almost anywhere on the roof is the addition of medium to large natural objects, such as branches or stones (these may need to be fastened down), or even rubble, all of which help to create different microclimates and microhabitats which may lead to greater species diversity. Similarly, branches can provide physical connections and shady habitats and serve as resting sites for birds to perch and as nesting structures. Bird or bat boxes can also be added to encourage species to nest and breed.
Recirculating bubbler fountain with no open water on green roof at 30 College Street, Toronto (Torrance, 2011) 12
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4.2 Design Strategies 4.2.1 Increase Depth of Growing Media In Toronto, The diversity of plants that can survive increases dramatically when the depth of substrate (growing media) is increased from 100 mm to 150 mm (4 to 6 inches). One option is to increase the depth across the entire roof, an alternative is to increase the depth of substrate on the parts of the roof that can support the additional load (e.g., above structural areas) and provide greater planting diversity on these areas. A list of plant species and minimum growing depth is provided in Appendix A.
DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
nesting and to collect mud for nesting material. Earthworms would need a loose, coarse, more organic growing media than typical green roof mineral mixes provide to survive. High organic growing media can be combined with low organic, mineral-based growing media across the roof. Gravel can also be used on bare areas on the roof.
vary granule size
vary mixtures
incorporate bare areas of gravel
4.2.3 Provide Topographic Variety 4.2.2 Vary Composition (Structure) of Growing Media Structure can play a role in supporting biodiversity by varying the granule size of the aggregates in the substrate and the spread of different mixtures upon the roof area. Soils often have a particular distribution of granules, and native soils can be analyzed in order to reproduce the range of granularity. Varying the composition of growing media creates opportunities for greater diversity of plant species and habitats, most notably insects and soil nematodes. For instance, some species of spiders, solitary bees and pest controlling wasps need bare, non-compacted, small particulate soil areas for
Topographic diversity increases soil depth and microclimatic variation. Sloped surfaces are typically drier at the top and wetter at the bottom. This variation creates an opportunity for different plant selection to correspond to this micro-hydrological regime. Topographic diversity can also be implemented using different heights of edging, modules and planters.
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4.2.4 Provide Microclimates
4.2.5 Diversify Plant Species
Objects, including building elements, provide microclimatic opportunities in the typically uniform full sun and dry condition found on green roofs. Areas in shade and below objects will be cooler and moister, providing habitat diversity opportunities, especially for insects and soil organisms.
Maximizing the diversity of plant species and plant life forms (succulents, herbaceous perennials, woody plants, coniferous, deciduous, etc.) has many benefits, increasing the opportunities for pollination and food, shade, nesting, perching, nutrients, etc. Depending on maintenance levels, which are typically minimal on green roofs, succession of plants overtime must be considered as a natural consequence (or benefit) of a diverse planting strategy.
rocks
plants
4.2.6 Provide Perching Habitat
lots
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buildings elements
Objects, such as rocks, logs, branches or constructed elements can be integrated into green roofs to attract birds and insects to perch. Some objects, such as logs and branches, may need to be secured to the roof. Metal should be avoided due to heat absorption.
rocks
forbs, grasses and shrubs
branches and platforms
logs
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
4.2.7 Provide Nesting Opportunities
4.2.8 Provide Water Source(s)
Elements to encourage nesting opportunities for birds and insects can be integrated into green roofs. Some insects and birds (e.g. killdeer) use bare areas of soils and gravel for nesting. Bird and bee houses require regular cleaning and maintenance if they are utilized. Some objects may need to be secured to the roof.
Water is one of the principle limiting resources for most species that would otherwise be able to use green roofs as permanent habitat. These effects are exacerbated given that green roofs are hotter and more exposed than most ground-level habitat. Puddles or vernal pools will not form or last long. For example, many bird species may find green roofs to be suitable nesting space, but once chicks hatch, periods of drought can be fatal. A source of water can be provided in two ways: either pumped or collected. Pumped and recirculated water features require energy and regular maintenance (cleaning, topping up with fresh water, seasonal closing, etc.). Rainfall can be collected in depressions and basins. Maintaining water on a roof, either natural from precipitation or artificially (with a pump or fresh water supply) may not be desirable from a building science perspective and can create habitat for mosquitoes.
Tall grasses and shrubs
Birdhouses
Logs and branches
Open soil areas
Bee nest boxes
basins
bird baths
water features
naturally pitted cap rock
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Green roof designed with many different depths of growing medium, as well as open soil areas, in order to support a diversity of trees, shrubs, grasses, forbs and succulents. ESRI Canada, Toronto (Torrance/Mulligan, 2010)
4.3 Design Analogues 4.3.1 Recreate Native Landscapes Green roofs can be designed to mimic almost any habitat and also provide an opportunity to recreate specific native landscapes. Habitats such as grasslands and herb communities are well suited to intensive roofs.
Green roof with 75mm to 500mm growing depths, deep enough to support a variety of native prairie plants. Design includes structures for perching and nesting and water feature to attract wildlife. Native Child & Family Services, Toronto (Torrance, 2009)
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Green roofs have been found to be broadly analogous to certain types of landscapes, from which plants are seemingly pre-adapted to the harsh green roof environment. Selecting plants from habitats that exhibit microclimatic characteristics similar to green roofs increase chances of discovering suitable plants. These include permanently open habitats such as rocky outcrops, cliffs, dunes, heathlands, and alvars.
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Four of these habitat types are potential analogues for green roof plant selection and growing media composition: tallgrass prairie, alvars, fens and sand barrens.
DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
palette. An overarching philosophy of maximizing species diversity and then allowing plants to colonize themselves will help build resiliency through adaptability into the green roof ecosystem. A list of plants and minimum soil depths is provided in Appendix A.
Tallgrass Prairie Defining Characteristics: • Grassland with variable cover of small woody shrubs and open-grown trees • Subject to seasonal extremes in moisture conditions • Tolerates spring flooding and summer drought • Regenerated by fire disturbance Growing Media Composition: • Unconsolidated mineral substrates with a soil depth of > 150mm • Typically consists of well-drained sands, loams, and sometimes clay Plant Selection: • Dominated by prairie grasses, forbs, sedges, small woody shrubs and open-grown trees Other Considerations: It is not wholly accurate to use the tallgrass prairie habitat as a template for green roof design, as species diversity is lower and conditions on extensive green roofs vary considerably from those found in a natural tallgrass prairie habitat. Soil depth is less then found in the natural habitat, conditions tend to be drier and windier and soil quality is poorer. For these reasons, grasses cannot establish their roots as extensively. Fire disturbance – a natural phenomenon that supports vegetative regeneration – is also absent on green roofs.
Tallgrass Prairie, Walpole Island First nation, Essex County, Ontario (J.L. Riley from Ecological Land Classification for Southern Ontario, 1998)
An alternative is to create a hybrid meadow/grassland plant community. If only a 100mm soil depth can be achieved, a much more limited number of plant species can be used. A minimum soil depth of 150 mm will support a greater diversity of species and thus a more comprehensive planting TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
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Alvars
Fens
Defining Characteristics: • naturally open landscapes with little or no tree cover • patchy distributions of loamy and sandy soils at heterogeneous depths • soil texture is generally a loam
Defining Characteristics: • open habitats • wet almost all year • soils are high in organic content (a result of decomposing plant material), contain peat, and are often saturated • support a wide diversity of plant and insect species
Growing Media Composition: • shallow depths (less than 20cm) • depressions interspersed among bare rocky patches • generally wet in the spring and severely dry in the mid-summer • contain distinctive species which are adapted to harsh green roof environments, as well there are many rare species Plant Selection: • patchy distribution of grasses and forbs Other Considerations Alvars have patchy distributions of loamy and sandy soils at heterogeneous depths, a result of natural depressions in the underlying limestone bed, and surrounding exposed rock. Soil texture is generally a loam. Green roofs using alvar habitat analogs as a design focus will want growing media with organic matter, shallow depths (less than 20cm) and depressions interspersed among bare rocky patches. These habitat analogs will need to be generally wet in the spring and severely dry in the mid-summer.
Growing Media Composition: • organic-rich soils, as deep as possible, with some aggregates Plant Selection: • dominated by sedges, grasses, forbs, mosses, and some woody plants Other Considerations: Buildings that produce high volumes of wastewater (e.g. air conditioners, industrial processes), are lower to the ground and less exposed, are good candidates for incorporating fen habitat analogs into their green roof design. It is not economically or environmentally feasible to use fen habitat as templates for green roof design if only potable water is available for irrigation. The best strategy is to route wastewater onto the roof, keeping it saturated as often as possible during the spring, summer, and fall seasons.
Alvar, Bruce Alvar Nature Reserve, Bruce County, Ontario (J.L. Riley from Ecological Land Classification for Southern Ontario, 1998) 18
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Fen, Emily River Fen, Victoria County, Ontario (J.L. Riley from Ecological Land Classification for Southern Ontario, 1998)
DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Sand Barrens
4.3.2 Design to attract specific fauna
Defining Characteristics: • restricted tree growth • full exposure to sun • poor soil quality Growing Media Composition: • sandy and well-draining • heterogeneous depths and a mix of larger aggregates Plant Selection: • slow-growing shrubby grassland and heathland mosaics, dotted with a high diversity of herbaceous plants • drought tolerant Other Considerations: It is recommended to not design an entire roof after the Sand Barren community, as sandy soils are more likely to erode from the rooftop by wind. Instead, patches of sand barren habitat can be considered. When patches are planted, use soil stabilizers and erosion control netting until the plants establish to minimize soil loss.
Green roofs can be designed to attract and support certain fauna, typically birds and insects, whether they are native, rare or require stopping points on a migration route. This can be done by designing the roof to provide certain features that these fauna require on the landscape, but not necessarily the complete habitat. Birds Urban development and loss of habitat have impacted travel distances, expended energies, and reduced the availability of food sources for migratory birds passing through. Green roofs provide vegetation where there would otherwise be none and create temporary foraging habitat for local and migratory birds. Grasses and herbaceous plants that produce numerous seed heads can provide invaluable energy sources for migratory birds. Perches and nesting boxes can provide opportunities for resting and breeding.
Sand Barren, Giant’s Tomb Island Nature Reserve, Simcoe County, Ontario (J.L. Riley from Ecological Land Classification for Southern Ontario, 1998)
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Migratory Birds in the City of Toronto A 2009 report Migratory Birds in the City of Toronto identifies the potential of green roofs as temporary stopover habitat for migratory species especially when flying over extensive urbanized areas en route to more suitable habitat. Green roofs might also pose a hazard to birds passing over the city by increasing its chance of colliding with reflective glass adjacent to the roof. The City’s Bird-Friendly Development Guidelines can be implemented on portions of buildings adjacent to green roofs to help reduce bird fatalities.
Bird-Friendly Development Guidelines Migratory Birds in the City of Toronto Green roof elements designed to attract birds, providing nesting and perching opporunities,
at University Hospital, Basel, Switzerland (Bass, 2003)
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Bees
DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
provide permanent nesting space for these species on rooftops.
There are many species of pollinators, including bees, flies, moths, and butterflies that can incorporate green roofs into their foraging ranges. Bees, in particular, being highly mobile, mostly polylectic (meaning, they can visit many different kinds of flowers), and adapted to spatially separate nesting and foraging resources, are very well suited to receive support from green roofs designed with foraging and nesting resources in mind. This is all the more important as bee populations decline worldwide. Bees need flowers for pollen and nectar, and green roofs with diverse plant palettes to prolong blooming are most valuable. In cities, wild bee diversity seems to positively respond to increases in total plant diversity. Roofs planted entirely with Sedum, or similar species, also provided pollen and nectar for many bees, but only flower for only a short period so act only as temporary resources. If one of the objectives is to keep honeybees on the green roof, water should be available at all times in buckets or pans, an open rain barrel, or preferably a continuous fresh water source. Honeybees need to collect large amounts of water to maintain healthy hives. The water is used to dilute honey to feed to larva, and to cool the hive through evaporation in hot weather. Interestingly, many pollinators are highly-mobile and adapted to spatially separated foraging and nesting areas. As such, many bees can reach green roofs and once there may find permanent (nesting and forage) or temporary (forage only) refuge; thereby incorporating green roofs into their foraging ranges. Since approximately 60 percent of Toronto’s bee species nest in the ground, green roofs designed to support bees might include areas of bare soil, soil topographic heterogeneity, and a plant community with an extended flowering period. Many other bees nest in stems and pre-existing cavities, so maintenance that includes not cutting plant stems down to the soil (leave 150 mm (6 inches) or more, if possible), adding dead wood as a design element, or even nestboxes, comprised of holes drilled into wood, or bundled reeds or paper tubes plugged at one end added as a roof feature could
Bee nesting box, 410 Richmond Street, Toronto (MacIvor, 2011)
Other Insects Green roofs may provide habitat for pollinating insects such as bees, flies, and butterflies, but also other functionally important invertebrates. These include those critical for nutrient cycling and decomposition, such as springtails, millipedes, beetles, and worms; predation of pest species by spiders, solitary wasps, dragonflies and damselflies; and many as food for other desirable species in cities, like birds. Although many urban invertebrates may only use a green roof habitat temporarily, some species, particularly those soil-dwellers important for nutrient cycling and decomposition can be permanent inhabitants, and so require some consideration in green roof planning to ensure populations can colonize and persist. Greater growing media depths, plant canopy, and features like logs, TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
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large stones or pavers are all important to reduce exposure and keep some areas slightly more damp and cool. This is essential for survival of soildwelling and low-mobility species during the driest and hottest times of the year.
close to a ravine could specify plants that will create an edge condition to the ravine and use existing plant communities to inform the selection of appropriate species on the roof to effectively expand the planted area onto the tableland.
Many highly-mobile, species like bees, butterflies, dragonflies, and birds can incorporate one or more green roofs, both intensive and extensive, into their foraging range. These species may source requirements for survival and reproduction from a green roof, such as food (pollen, nectar, prey), or shelter (nesting material, locations, oviposition and metamorphosis sites).
The table on the following page outlines design objectives and strategies for green roofs in specific locations in the City of Toronto.
Species that find permanent refuge on an extensive green roof may have low resource requirements for survival and successful reproduction. For example, some small ground-nesting eusocial and solitary Lasioglossum bees can provision larvae with pollen and nectar in very shallow, welldraining sunny soils. These bees are very effective pollinators, but due to their small size can meet all of their foraging requirements from small patches of flowering plants of different species. Other desirable, permanently inhabiting green roof species include spiders, predatory beetles, and solitary wasps each of which effectively collect and feed on pest insects that inflict damage and harm green roof plants. A list of plants used by butterflies and caterpillers is provided in Appendix C.
4.3.3 Design to support adjacent ecosystems Green roofs located near or adjacent to natural heritage areas can be designed to expand and support these neighbouring ecosystems. Green roofs can act as transition zones or buffers between natural habitats and the surrounding urban area and perform ecosystem services such as providing food for pollinators and resting, feeding and breeding space for local and migratory birds. Green roofs located near or adjacent to natural heritage areas should look to how their design can enhance and improve the condition of the natural habitats. For example, new development
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Design Objectives and Strategies for Green Roofs in Specific Locations in Toronto Extensive Green Roof Adjacent to Rosedale Ravine, Toronto (Torrance, 2008)
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Design Objectives and Strategies for Green Roofs in Specific Locations in Toronto
Green Roof Location
Objectives
Design Strategies
Areas adjacent to forest habitat (e.g., river valleys, High Park, Rouge Park).
Enhance/buffer adjacent ecozones and link green roofs to forest ecosystems at grade level. Beneficial matrix influence through climate and hydrological mitigation to buffer adjacent forest ecosystems.
Create higher order “climax� ecosystems; use small shrub and tree species.
Provide perching/ breeding/ feeding opportunities for migratory birds, butterflies and insects.
Enhance property perimeter regions at grade level to scale up available shrubs and other forest constituents.
Species for Conservation or Protection Forest Interior birds, rare plants, native shrubs/small trees, pollinators including butterflies (along with other trophic benefactors eg. microbial soil constituents).
Design for aggregations of green roofs on clusters of buildings.
Provide habitat for native plants. Areas adjacent to Lake Ontario shoreline, river valley corridors.
Extend perching/ breeding/ feeding zones for migratory birds, butterflies and insects. Provide habitat for native meadow/prairie plants
Areas adjacent to meadow habitat (e.g., along hydro corridors).
Extend meadow/grassland habitats and support zones for migratory birds, butterflies and insects. Provide habitat for native meadow/prairie plants.
Meadow grasses (native and non-native) perennials + tall grass prairie species; also try pre-vegetated mat systems with augmentations in substrate depths/shapes/ mounds where practical. Include plants that produce abundant seeds to feed early spring migrants.
Migratory birds and butterflies, native plants, insects and other pollinators (along with other trophic benefactors).
Meadow, grasslands or pre-vegetated mats with augmentations to substrate depth as practical.
Meadow plants, grass and shrubland birds, butterflies and invertebrates.
Alvar species.
Alvar species and possibly some meadow marsh species where water is retained more.
Source: Using Green Roofs to Enhance Biodiversity in the City of Toronto, 2010. TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Sources / Resources Bird-Friendly Development Guidelines. 2007. City of Toronto. http://www.toronto.ca/planning/environment/guidelines.htm City of Toronto Natural Heritage Study. 2001. City of Toronto and Toronto and Region Conservation Authority. http://www.toronto.ca/planning/environment/pdf/natural_heritage/natural_text1.pdf Ecological Land Classification for Southern Ontario. 1998. First Approximation and Its Application. H. T. Lee, W.D. Badowsky, J.L. Riley, J. Bowles, M. Puddister, P. Uhig, S. McMurry. 1998. Ontario Ministry of Natural Resources. Southcentral Science Section, Science Development and Transfer Branch. SCSS Field Guide FG-02. Migratory Birds in the City of Toronto. 2009. Prepared for Toronto City Planning. Prepared by North-South Environmental Inc. and Dougan & Associates. http://www.toronto.ca/planning/environment/pdf/migratory_birds_15aug09_small.pdf Toronto Green Roofs http://www.toronto.ca/greenroofs/index.htm Toronto Green Roof Construction Standard (Article IV of Toronto Municipal Code Chapter 492 Green Roof) http://www.toronto.ca/legdocs/municode/1184_492.pdf Toronto Green Roof Construction Standard Supplementary Guidelines. http://www.toronto.ca/greenroofs/pdf/GreenRoof-supGuidelines.pdf Toronto Green Standard http://www.toronto.ca/planning/environment/index.htm Toronto Municipal Code Chapter 492 Green Roof http://www.toronto.ca/legdocs/municode/1184_492.pdf Toronto Official Plan. 2010 http://www.toronto.ca/planning/official_plan/pdf_chapter1-5/chapters1_5_dec2010.pdf Report on the Environmental Benefits and Costs of Green Roof Technology for the City of Toronto. 2005. Prepared For City of Toronto and Ontario Centres of Excellence – Earth and Environmental Technologies (OCE-ETech). Prepared By Ryerson University Professors Dr. Doug Banting, Professor Hitesh Doshi, Dr. James Li, Dr. Paul Missios and Students Angela Au, Beth Anne Currie, Michael Verrati. http://www.toronto.ca/greenroofs/ pdf/fullreport103105.pdf Using Green Roofs to Enhance Biodiversity in the City of Toronto. 2010. A Discussion Paper Prepared for Toronto City Planning. Beth Anne Currie and Brad Bass. http://www.toronto.ca/greenroofs/pdf/greenroofs_biodiversity.pdf
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Appendix A: Recommended Plant Species Plant species should be selected first for their ability to survive the conditions they will grow in, considering: • depth of growing media • slope of roof, if any • amount of sunlight available • type of irrigation that will be provided (manual, automatic, none) • wind exposure • maintenance levels • location (i.e. adjacent to natural heritage area or not) • program (desired look, approach, program desired) • hardiness zone (depending on roof level, at least one zone hardier than Toronto’s hardiness zone of 6) • availability in the nursery trade • conformance with Green Roof Bylaw • Succession of plants over time Once plant species are determined based on the above criteria, the type of growing media should be selected: • low organic matter content i.e. FLL, <10% by weight • high organic matter content >10% by weight • The use of native and adaptive species should be maximized.
Based upon data collected in 2004 and 2005, the Toronto and Region Conservation Authority developed a list of native plants for a green roof environment in Toronto: http://www.toronto.ca/greenroofs/pdf/plant_suggestions2007.pdf. The following plants are recommended for use in Toronto green roofs:
Native Grasses Botanical Name Bouteloua curtipendula Bouteloua gracilis Carex Pennsylvannia,Nigra Chasmanthium latifolium Deschampsia cespitosa Panicum virgatum Schizachyrium scorparium
Common Name Side-oats Grama Blue grama grass Sedge Northern Sea Oats Tufted Hair Grass Switch Grass Little Bluestem
Min. Depth 150mm 100-150mm 150mm 100-150mm 100-150mm 100-150mm 100-150mm
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Native Forbs Botanical Name Asclepias tuberose Aster laevis Campanula rotundifolia Echinacea pallida Epilobium angustifolium Eupatorium purpureum Eupatorium perfoliatum Gentiana andrewsii Geum triflorum Hedyotis longifolia Liatris cylindracea Liatris spicata Lobelia siphilitica Lobelia cardinalis Lupinus perennis Lysimachia quadriflora Maianthemum stellatum Monarda didyma Monarda fistulosa Penstemon digitalis Polygonatum pubescens Physostegia virginiana Rudbeckia hirta Ratibida pinnata Solidago ptarmicoides Solidago squarrosa Verbena simplex Verbena stricta Veronicastrum virginicum
Common Name Butterfly Milkweed Smooth Aster Harebell Pale Purple Coneflower Fire-weed Joe-Pye Weed Boneset Bottle Gentian Prairie Smoke Long-leaved Bluets Cylindric Blazing Star Dense Blazing-star Great Blue Lobelia Cardinal flower Wild Lupine Prairie Loosestrife Starry False Solomon’s Seal Beebalm (Oswego Tea) Wild Bergamot Foxglove Beardtongue Downy Solomon’s Seal Obedient Plant Black-eyed Susan Gray Headed Coneflower Upland White Goldenrod Stout Goldenrod Slender Vervain Hoary Vervain Culver’s Root
Min. Depth 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm
Common Name Common Juniper Creeping Juniper White Cedar
Min. Depth 300mm 300mm 300mm
Native Evergreens Botanical Name Juniperus communis var. depressa Juniperus horizontalis Thuja occidentalis 26
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Native Woody Plants Botanical Name Amelanchier laevis Amelanchier stolonifera Aronia melanocarpa Cephalanthus occidentalis Celastrus scandens Cladrastis lutea Cornus alternifolia Cornus amomum Cornus canadensis Cornus racemosa Cornus sericea Diervilla lonicera Hamamelis virginiana Hypericum kalm. Kalm’s Ilex verticillata Myrica pennylvanica Parthenocisus virginiana Physocarpus opulifolius Rhus aromatica Rhus glabra Salix exigua Sambucus canadensis Sambucus pubens Spirea alba Spirea tomentosa Symphoricarpus albus Viburnum dentantum Viburnum lentago Viburnum trilobum Vitis riparia
Common Name Saskatoon Berry Smooth Serviceberry Chokeberry Buttonbush Bittersweet Yellowwood Pagoda Dogwood Silky Dogwood Bunchberry Grey Dogwood Red Osier Dogwood Bush Honeysuckle Witch Hazel St. John’s Wort Winter Berry Bayberry Virginia Creeper Ninebark Fragrant Sumac Smooth Sumac Sandbar Willow Green Elder Scarlet Elder Narrow Leaf Meadowsweet Steeplebush Snowberry Arrowwood Sheepberry Highbush Cranberry Riverbank Grap
Min. Depth 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 150mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm 200mm
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Non-Native Grasses Botanical Name Calamagrostis X acutiflora ‘Karl Foerster’ Calamagrostis X acutiflora ‘Overdam’
Common Name Karl Foerster Feather Reed Grass Overdam Feather Reed Grass
Min. Depth 150mm 150mm
Common Name Chinese Astilbe Chives Bergenia Bachelor’s Button Snow-in-Summer Maiden Pinks Eastern Purple Coneflower Blue Globe Thistle Bloody Cranesbill Daylily Siebold Hosta Dwarf Arctic Iris English Lavender Summer Phlox Moss Phlox Coneflower Lemon Thyme Creeping Thyme Silver Speedwell
Min. Depth 150mm 100-150mm 150mm 100-150mm 100-150mm 100-150mm 150mm 150mm 100-150mm 100-150mm 150mm 100-150mm 100-150mm 100-150mm 100-150mm 150mm 100-150mm 100-150mm 150mm
Common Name Sibirica Pearls Isanti Red-Osier Dogwood Annabelle Bush Cinquefoil Wineleaf Cinquefoil
Min. Depth 200mm 200mm 200mm 200mm 200mm
Non-Native Forbs Botanical Name Astilbe chinensis Allium shoenoprasum Bergenia cordifolia Centaurea montana Cerastium tomentosum Dianthus deltoides Echinacea purpurea Echinops ritro Geranium sanguineum Hemerocallis sp. Hosta sieboldiana Iris setosa Lavandula angustifolia Phlox paniculata Phlox subulata Rudbeckia nitida Thymus citriodorus Thymus serphyllum Veronica incana
Non-Native Woody Plants Botanical Name Cornus alba Cornus sericea ‘isanti’ Hydrangea arborescens Potentilla fruticosa Potentilla tridentata ‘Nuuk’
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Non-Native Woody Plants (Continued) Prunus X cistena Rhodendron ‘Aglo’ Spirea bumalda ‘Goldmound’ Syringa vulgaris Weigela florida ‘French Lace’
Purple Leaf Sand Cherry Aglo Rhododendron Spirea Goldmound Common Liliac French Lace Weigela
200mm 200mm 200mm 200mm 200mm
Common Name Yarrow Pearly everlasting Columbine Butterfly Milkweed Smooth Blue Aster New England Aster Harebell, Bluebell Narrow Leafed Coneflower Pale Purple Coneflower Joe Pye Weed Horsetail Grass Strawberry Willow-leaved Sunflower Common sneezeweed Cylindric Blazing Star Dense Blazing-star Great Blue Lobelia Cardinal flower Beebalm (Oswego Tea) Wild Bergamot Foxglove Beardtongue Obedient Plant Black-eyed Susan Slender Vervain Hoary Vervain Culver’s Root
Min. Depth 100-150mm 150mm 100-150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 100-150mm 100-150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 150mm 100-150mm 150mm 150mm
Forbs – Full Sun Botanical Name Achillea sp Anaphalis margaritacea Aquilegia Canadensis Asclepias tuberosa Aster laevis Aster nova-angeliae Campanula rotundifolia Echinacea angustifolia Echinacea pallida Eupatoriummac purpureum Equisetum hymenale Fragaria virginia Virginia Helianthus salicifolius Helenium autumnale Liatris cylindracea Liatris spicata Lobelia siphilitica Lobelia Cardinalis Monarda didyma Monarda fistulosa Penstemon digitalis Physostegia virginiana Rudbeckia hirta Verbena simplex Verbena stricta Veronicastrum virginicum
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Non-Native Plants - Full Sun Botanical Name Aster tararicus ‘Jindai’ Aster tararicus Bergenia Cordifolia Centaurea Montana Cerastium tomentosum Coreopsis tripteris Coreopsis verticillata Dianthus deltoides Campion (Silene) Echinacea purpurea Echinops ritro Euphorbia Geranium maculatum Geranium psilosteum Geranium pratense Geranium sanguineum Gaillardia grandiflora Geum Hemerocallis Hosta sieboldiana Iris germanica Iris setosa Lavandula angustifolia Leucanthemum X superbum Nepeta X faassenii Phlox subulata Rudbeckia Salvia X sylvestris Sedum album Sedum ellacombianum Sedum ewersii Sedum hybrid ‘Autumn Joy’ Sedum kamschaticum
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Common Name Dwarf Tatarian Aster Tartarian Aster Heart-leaved Bergenia Mountain Bluet Snow-in-summer Tall Tickseed Thread-leaved Coreopsis Maiden Pinks Moss Pinks Purple Coneflower Globe Thistle Crown-of-thorns Wild Geranium Armenian Cranesbill Meadow Cranesbill Bloody Geranium Blanketflower Avens Daylily (Sun Loving Hostas) German Iris Dwarf Arctic Iris English Lavender Shasta Daisy Catmint Creeping Phlox Goldsturm Coneflower Sage Carpet Stonecrop Sedum ellacombianum Pink Mongolian Stonecrop Autumn Joy Sedum kamschaticum
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Min. Depth 150mm 150mm 150mm 150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm
DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Non-Native Plants - Full Sun (Continued) Sedum sexangulare Sedum spectabilis Solidago sphacelata X Solidaster luteus Sedum spurium Stachys byzantina Thymus serphyllum Thymus X citriodorus Veronica longifolia Veronica noveboracensis
Tasteless Stonecrop Showy Stonecrop Dwarf Goldenrod Solidaster Dragon’s Blood Lamb’s ears Creeping Thyme Lemon Thyme Long-leaved Speedwell Ironweed
100-150mm 150mm 150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm 100-150mm
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Appendix B: Plant Species to Avoid City of Toronto Bylaw No.583-2009 492-9 L states that vegetation on a green roof shall not include any noxious weeds as defined in Ontario Regulation 1096 under the Weed Control Act (see table below). In addition the following plant species also should be avoided:
•
Medicago spp. (Black Medick), Capsella sp. (Shepherd’s Purse), Cerastium sp. (Chickweeds) will each grow exponentially and then undergo massive die-off during periods of drought. Each set large numbers of seeds and have incredible spread.
• Digitaria spp. (Crabgrasses), Alliaria sp. (Garlic Mustards), Ambrosia sp. (Ragweed) all very drought tolerant, but highly competitive and spread very fast. • Chenopodium album (Lamb’s Quarter) - very drought tolerant - staying green when everything else is brown - but sets many seeds and spreads fast.
DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Noxious Weeds (Ont. Regulation 1096 – Weed Control Act) Item Common Name
Botanical Name
1. 2. 3. 4. 5. 5.1 6. 7. 8. 9. 10. 11. 12.
Barberry, common Buckthorn, European Carrot, wild Colt’s-foot Dodder spp. Giant Hogweed Goat’s-beard spp. Hemlock, poison Johnson grass Knapweed spp. Milkweed spp. Poison-ivy Proso millet, black-seeded
13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.
Ragweed spp. Rocket, yellow Sow-thistle, annual, perennial Spurge, Cypress Spurge, leafy Thistle, bull Thistle, Canada Thistle, nodding, spp. Thistle, Russian Thistle, Scotch Vetchling, tuberous
Berberis vulgaris L. Rhamnus cathartica L. Daucus carota L. Tussilago farfara L. Cuscuta spp. Heracleum mantegazzianum Tragopogon spp. Conium maculatum L. Sorghum halepense (L.) Persoon Centaurea spp. Asclepias spp. Rhus radicans L. Panicum miliaceum L. (black-seeded biotype) Ambrosia spp. Barbarea spp. Sonchus spp. Euphorbia cyparissias L. Euphorbia esula L. (complex) Cirsium vulgare (Savi) Tenore Cirsium arvense (L.) Scopoli Carduus spp. Salsola pestifer Aven Nelson Onopordum acanthium L. Lathyrus tuberosus L.
http://www.e-laws.gov.on.ca/html/regs/english/elaws_regs_901096_e.htm
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Appendix C: Plants Used by Butterflies and Caterpillars These are some common plants used by butterflies for nectar and by caterpillars as food in the Toronto area. This list is not comprehensive. Where several species (spp.) in a genus are suitable, only the genus name is given (e.g., Asclepias spp. for various milkweed species). The status of different species in a genus may vary (i.e., some may be invasive while others are not). Some species may not be suitable because they can be aggressive or invasive.
• • • •
Native plants grew in our area before the arrival of Europeans. Cultivated plants are introduced species that grow in our area only with human assistance. Naturalized plants are introduced species that survive without human assistance and now reproduce here. Invasive plants are naturalized species that negatively impact native biodiversity by reproducing aggressively and taking over natural habitats, to the exclusion of other plants. spp. = various species in the genus
Source: Butterflies of Toronto: A Guide to their Remarkable World. City of Toronto Biodiversity Series. City of Toronto, 2011.
Caterpillar Plants (Host Plants) •• • • •
Common Name
Scientific Name
speckled alder hog peanut pearly everlasting bluestem
Alnus incana Amphicarpaea bracteata Anaphalis margaritacea Andropogon spp.
Species whose caterpillars use this plant
• dill • burdock • Dutchman’s pipe • milkweed ••• birch ••• thistle • sedge
Harvester (woolly aphids) Silver-spotted Skipper, Northern Cloudywing American Lady Leonard’s Skipper, Crossline Skipper, Delaware Skipper, Common Wood-Nymph Anethum graveolens Black Swallowtail Arctium spp. Painted Lady Aristolochia durior Pipevine Swallowtail Asclepias spp. Monarch Betula spp. Compton Tortoiseshell Carduus spp., Cirsium spp. Painted Lady Carex spp. Broad-winged Skipper, Black Dash, Dion Skipper,
• • •• •• • •
New Jersey tea hackberry turtlehead dogwood crown vetch native hawthorn
Ceanothus americanus Celtis occidentalis Chelone spp. Cornus spp. Coronilla varia Crataegus spp.
• • •
Queen Anne’s lace tick trefoil fennel
Daucus carota Desmodium spp. Foeniculum vulgare
Dun Skipper, Eyed Brown
Mottled Duskywing, Summer Azure
American Snout, Tawny Emperor, Question Mark
Baltimore Checkerspot Spring Azure, Summer Azure Wild Indigo Duskywing Striped Hairstreak, White Admiral/Red-spotted Purple Black Swallowtail Northern Cloudywing, Eastern Tailed-Blue Black Swallowtail
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Common Name Scientific Name
• •• • • •• • • • • • timothy • ninebark • English plantain • native pine • bluegrass • native poplar
Gerardia spp. Helianthus spp. Linaria vulgaris Lupinus perennis Malus spp. Medicago sativa Melilotus spp. Panicum spp. Petroselinum crispum Phleum pratense Physocarpus opulifolius Plantago lanceolata Pinus spp.
••
cherry/plum
Prunus spp.
• •• • • • • ••
hoptree oak black locust curled dock sheep sorrel
Ptelea trifoliata Quercus spp. Robinia pseudoacacia Rumex crispus Rumex acetosella
• • •• • •• ••
sassafras wild mustard aster clover elm nettle
Sassafras albidum Sinapis arvensis spp. Symphyotrichum spp. Trifolium spp. Ulmus spp. Urtica spp., Laportea spp.
•• •• ••
viburnum vetch violet
Viburnum spp. Vicia spp. Viola spp.
• •
pansy prickly ash
Viola wittrockiana Zanthoxylum americanum
gerardia wild sunflower butter-and-eggs wild lupine apple alfalfa sweet-clover panic grass parsley
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rue willow
Poa pratensis Populus spp.
Ruta graveolens Salix spp.
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Species whose caterpillars use this plant
Common Buckeye Silvery Checkerspot Common Buckeye Wild Indigo Duskywing, Karner Blue White Admiral/Red-spotted Purple Clouded Sulphur, Orange Sulphur, Eastern Tailed-Blue Orange Sulphur, Summer Azure, Silvery Blue
Tawny-edged Skipper, Northern Broken-Dash, Hobomok Skipper
Black Swallowtail European Skipper, Long Dash Spring Azure, Summer Azure Common Buckeye Eastern Pine Elfin
Long Dash, Hobomok Skipper, Common Ringlet, Little Wood-Satyr Dreamy Duskywing, Canadian Tiger Swallowtail, Red-spotted Purple/White Admiral, Viceroy Canadian Tiger Swallowtail, Eastern Tiger Swallowtail, Coral Hairstreak, Striped Hairstreak, Spring Azure, Cherry Gall Azure, Red-spotted Purple/White Admiral
Giant Swallowtail
Juvenal’s Duskywing, Edwards’ Hairstreak, Banded Hairstreak
Silver-spotted Skipper American Copper, Bronze Copper American Copper
Black Swallowtail, Giant Swallowtail Dreamy Duskywing, Red-spotted Purple/White Admiral, Viceroy, Compton Tortoiseshell, Mourning Cloak, Green Comma
Spicebush Swallowtail Mustard White Pearl Crescent, Northern Crescent Clouded Sulphur, Eastern Tailed-Blue Mourning Cloak, Question Mark, Eastern Comma Red Admiral, Milbert’s Tortoiseshell, Question Mark, Eastern Comma
Spring Azure, Summer Azure Clouded Sulphur, Orange Sulphur, Eastern Tailed-Blue, Silvery Blue Variegated Fritillary, Silver-bordered Fritillary, Meadow Fritillary, Great Spangled Fritillary Variegated Fritillary Giant Swallowtail
DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Nectar Plants SPRING FLOWERING (March – early June) Common Name
•• serviceberry •• dogwood ••• hawthorn • fleabane • wild strawberry • dame’s rocket •• apple • ninebark ••• buttercup •• blackberry/raspberry • elderberry • cup plant • lilac • dandelion • coltsfoot •• thyme ••• viburnum •• violet
Scientific Name Amelanchier spp. Cornus spp. Crataegus spp. Erigeron spp. Fragaria virginiana Hesperis matronalis Malus spp. Physocarpus opulifolius Ranunculus spp. Rubus spp. Sambucus spp. Silphium perfoliatum Syringa spp. Taraxacum officinale Tussilago farfara Thymus spp. Viburnum spp. Viola spp.
SUMMER FLOWERING (June – August) Common Name
• chives • dogbane •• milkweed • butterfly bush • virgin’s bower • coreopsis • purple coneflower •• Joe-Pye weed • heliotrope • lantana •• blazing star • purple loosestrife • alfalfa • sweet-clover ••• mint • bee-balm • wild bergamot • catnip •• phlox •• cinquefoil ••• buttercup •• prairie coneflower • staghorn sumac •• black-eyed Susan •• tall coneflower •• • • • • • •• •• •
Scientific Name
Allium schoenoprasum Apocynum spp. Asclepias spp. Buddleja davidii Clematis virginiana Coreopsis spp. Echinacea spp. Eupatorium purpureum Heliotropium spp. Lantana spp. Liatris spp. Lythrum salicana Medicago sativa Melilotus spp. Mentha spp. Monarda didyma Monarda fistulosa Nepeta cataria Phlox spp. Potentilla spp. Ranunculus spp. Ratibida spp. Rhus typhina Rudbeckia hirta Rudbeckia laciniata brown-eyed coneflower Rudbeckia triloba rue Ruta graveolens salvia Salvia spp. scabiosa Scabiosa spp. clover Trifolium spp. heliotrope Valeriana officinalis vervain Verbena spp. ironweed Vernonia spp. zinnia Zinnia spp.
FALL FLOWERING (September – October) Common Name • spotted knapweed •• boneset • showy stonecrop • goldenrod •• aster
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Scientific Name Centaurea maculosa Eupatorium perfoliatum Sedum spectabile Solidago spp. Symphyotrichum spp.
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