Download City of Toronto guidelines for Biodiverse Green Roofs

DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Acknowledgements:
Prepared by:
Scott Torrance Landscape Architect Inc.,
with: 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
2013
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Table of Contents
1.0 Introduction and Background
5
2.0 Natural Heritage and Biodiversity Objectives
6
3.0
Opportunities and Constraints
8
3.1 Extensive and Intensive
8
3.2 Roof Types 10
3.3 Native Vs Non Native
10
3.4 Invasive Species
10
4.0 Design Guidelines
11
4.1 Design Factors
11
4.1.1 Depth, Topography and Composition of Growing Media
11
4.1.2 Vegetation Diversity
11
4.1.3 Structures
12
4.2 Design Strategies
13
4.2.1 Increase Depth of Growing Media
13
4.2.2 Vary Composition (Structure) of Growing Media
13
4.2.3 Provide Topographic Variety
13
4.2.4 Provide Microclimates
14
4.2.5 Diversify Plant Species
14
4.2.6 Provide Perching Habitat
14
4.2.7 Provide Nesting Opportunities
15
4.2.8 Provide Water Source(s)
15
4.3 Design Analogues
16
4.3.1 Recreate Native Landscapes
16
4.3.2 Design to Attract Specific Fauna
19
4.3.3 Design to Support Adjacent Ecosystems
22
Sources/Resources
24
Appendix A: Recommended Plant Species
25
Appendix B: Plant Species to Avoid
33
Appendic C: Plants used by Butterflies and Caterpillers
35
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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
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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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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.
Example of hybrid meadow/grassland community, extensive green roof, 150 mm
depth at Jackman Public School, Toronto (McGlade, 2011)
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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.
TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
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.
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.
4.1.3Structures
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)
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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.
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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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
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
TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
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.
TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Four of these habitat types are potential analogues for green roof plant
selection and growing media composition: tallgrass prairie, alvars, fens and
sand barrens.
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
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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)
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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)
TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
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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TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Bees
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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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
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
22
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
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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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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
30
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
TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
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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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
Appendix B: Plant Species to Avoid
Noxious Weeds (Ont. Regulation 1096 – Weed Control Act)
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.
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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DESIGN GUIDELINES FOR BIODIVERSE GREEN ROOFS
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.
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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)
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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,
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New Jersey tea
hackberry
turtlehead
dogwood
crown vetch
native hawthorn
Ceanothus americanus
Celtis occidentalis
Chelone spp.
Cornus spp.
Coronilla varia
Crataegus spp.
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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
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• 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.
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cherry/plum
Prunus spp.
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hoptree
oak
black locust
curled dock
sheep sorrel
Ptelea trifoliata
Quercus spp.
Robinia pseudoacacia
Rumex crispus
Rumex acetosella
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sassafras
wild mustard
aster
clover
elm
nettle
Sassafras albidum
Sinapis arvensis spp.
Symphyotrichum spp.
Trifolium spp.
Ulmus spp.
Urtica spp., Laportea spp.
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viburnum
vetch
violet
Viburnum spp.
Vicia spp.
Viola spp.
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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.
TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
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
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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
TORONTO CITY PLANNING ZONING BYLAW AND ENVIRONMENTAL PLANNING
Scientific Name
Centaurea maculosa
Eupatorium perfoliatum
Sedum spectabile
Solidago spp.
Symphyotrichum spp.
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