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Archive for ‘January, 2017’

Common Plant UsedGreen roofs have become increasingly popular in cities. They provide a wide range of benefits such as reducing cooling costs, providing storm water management and being beautiful. One of the most desirable benefits of green roofs is their ability to providing natural habitat for local wildlife and pollinators. Green roofs provide sanctuaries for birds and insects in traditionally hostile urban environments and birds have even been recorded to use green roofs as nesting sites.

However, the most common plant used on green roofs are sedums. Sedums are non-native, succulent plants. They are used because they are low-lying, drought resistant and can be grown in mats which make greening a roof less heavy or time intensive to install. While Sedums do provide some benefits of reducing energy use and helping to manage storm water, they do very little in terms of sustainability and providing viable habitat for wildlife.  As an article in Scientific American put it, “A roof planted with sedum […] is no greener, from the standpoint of sustainability, than is ordinary tar or asphalt.”[1]

The low lying, tightly bunched nature of sedums does not provide the habitat the birds require. Wild flowers and grasses are more suited to the needs of nesting birds. Additionally, native plants provide food for the birds in the form of seeds and the insects that the plants attract. Sedums do not. Instead, the non-native plants tend to attract non-native insect species. The Green Roof Innovation Testing Laboratory at the University of Toronto found that Sedum green roofs were attracting non-native bee species, and while native bee species did use the sedums, they were more likely to be pollinating native plant species.

Brown Eyed SusanNative plants have the advantage that they have co-evolved with the local species. Many native pollinators feed exclusively on particular plants, meaning Sedums can never replace the role of the native plant. Local plant species are finely tuned to provide the habitat and food that the wildlife needs, and to support the populations throughout the season. Wildflowers bloom at different points throughout the season, so that there is a continuous food supply. Flowers in spring and summer attract insects which baby birds need, and then in fall plants produce berries and seeds that sustain the bird populations throughout the winter.

Native plants are the right fit for green roofs as these species are ideally suited to the local environment. Find nurseries that have sourced seeds from your seed zone, and you’ll know that the plants will survive whatever weather is thrown at them. Additionally, the variety in shapes, sizes and colours of native species can keep things interesting by creating a dazzling display that changes throughout the season. Many native prairie grasses and wildflowers do well in the heat and the sun that green roofs are exposed to. Additionally, there are many species whose roots systems do well in 4 to 6 inches of soil, lending them well to the shallow growing conditions of green roofs.

Fragaria VirginianaCheck out the city of Toronto’s Guidelines for Biodiverse Green Roofs[2] for some plant suggestions. One great species the report suggests is Wild Strawberry (Fragaria virginiana). This plant requires only 4 inches of soil, is low growing, produces fruit to feed birds and has beautiful dense foliage that turns red in fall.

In 4 to 6 inches of soil, many different grasses and meadow flowers can establish themselves. Plant a mix of species to increase the diversity, which in turn will provide more services for wildlife. Take a look at our seed mixes for inspiration on plants that do well together. Our Shallow Groundcover mix is ideally suited for green roofs, because their root systems do well in shallow soil. It includes plants such as Slender Wheat Grass (Elymus trachycaulus), Brown Eyed Susan (Rudbeckia hirta), Evening Primrose (Oenothera biennis), and Dwarf Blazing Star (Liatris cylindracea).

If you’re considering a green roof, talk to your designer about using native plants!

[1] https://www.scientificamerican.com/article/why-manhattans-green-roofs-dont-work-how-to-fix-them/


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Photo Credit: Arnold Aroboretum

The Kentucky Coffee Tree (Gymnocladus dioicus) is produced by St. Williams Nursery and Ecology Centre and grown in a variety of formats and sizes.  This unique deciduous tree is currently on the province of Ontario’s Species at Risk List as “Threatened” as of 2008 when the Endangered Species Act took effect.

The Kentucky Coffee tree grows 15-25 metres high and produces leaves as big as 60×90 centimetres, which are considered the largest leaves produced by any Canadian tree.  The fruit produced comes in a bean-like pod and contains four to seven seeds that remain on the tree throughout the winter.

The two main threats to the Kentucky Coffee tree are lack of suitable habitat and poor seed production.  In the latter, Male and Female flowers are produced on separate trees and unless these trees are growing in proximity of each other the trees will not produce seeds.

Interesting Facts:

  • Part of Gymnocladus dioica means “naked branch”, this is because the tree spends up to nine months of the year without any leaves.
  • Kentucky Coffee tree seeds are toxic to mammals. However, elephants are known to devour similar seed pods, and because of this it has been hypothesized that the Mastodons that once roamed the earth may have consumed these pods.

St. Williams Nursery and Ecology Centre has Kentucky Coffee (Gymnocladus dioica) available in the following formats at a variety of heights:

  • 1 year plug liner
  • Bareroot Field Transplants Liners
  • Potted Stock

For more information click here

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SWNaEC-logo-v2As we head into 2017 I am proud of all that we have accomplished at St. Williams Nursery and Ecology Centre over the past six years.  We have achieved much in pursuit of our mission to help preserve and restore Ontario’s natural biodiversity.  We have brought together some of the leading conservation scientists in the province and have successfully transformed a conventional forestry seedling nursery into one of the largest conservation nurseries in North America for our cause.  At St. Williams Nursery and Ecology Centre, we now produce millions of  wild-type source identified native plants (trees, shrubs, and forbs – grasses, sedges,  wildflowers, ferns and aquatic plants) and thousands of kilograms of native seed mixes that are the foundation for ecological restoration and biodiversity conservation projects.  Our native plants and seed have been planted throughout the province on our own ecological restoration projects such as the Highway 407East Habitat Compensation Project as well as by many conservation partners including Conservation Authorities, urban foresters, ecologists, government agencies, park managers, highway managers, school groups, NGOs and private citizens.

The conservation of native biodiversity remains a serious environmental challenge, and one that is complicated by global warming.  The landscape and horticultural industry as a whole in North America does not have a good track record when it comes to conserving native biodiversity.  Historically, the nursery industry has too often promoted exotic species over natives, and unwittingly has introduced many harmful exotic diseases (e.g., Dutch Elms Disease, Chestnut Blight) and invasive species (e.g., European Buckthorn, Phragmites) that have significantly impacted our native species and natural ecosystems.  An important aspect of biodiversity conservation now is to preserve local genemonarchtic biodiversity of native plants by collecting seed from wild populations and propagating new plants for restoration, landscaping and gardening.  It is essential that we restore and maintain healthy native plant communities in our landscapes in order to preserve the natural biodiversity of our province and country.  St Williams Nursery and Ecology Centre will continue to do our part as a leading biodiversity conservation organization in Ontario, tracking and monitoring native plant populations, and growing source-identified seed and plants for conservation.  I am excited to announce our new initiative to develop a Native Species Conservation Network seed database for Ontario in 2017 which will allow us to better work with more conservation partners to achieve our biodiversity conservation goals.  Biodiversity conservation is a big undertaking and we will require many partners  to work with us to plant source-identified wild type native plants in their landscapes, workplaces, parks and gardens…let’s bring nature home.

Yours in conservation,

Allan Arthur, M.Sc.
President, Sr Ecologist
St Williams Nursery and Ecology Centre

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