If you are planting tallgrass as garden plants consider where you live and what your surroundings are. If you are adjacent to a prairie area, don’t use plants that aren’t from your region. Connect with Tallgrass Ontario or your local naturalist group about the best place to get native plants for your area. Non natives (Invasive Species) are a huge problem and it is best not to plant them.
Garden centres and nurseries often sell plants noted as being native but are often from outside the province or country and can be varieties of the native plants. Don't hesitate to ask questions when purchasing your plants and inquire about where the garden centre acquires their plants from.
Check out the Tallgrass Ontario guide to tallgrass prairie and savanna plants in the ID a Grassland section.
Other sources of information:
For seed and plant sources, The Society for Ecological Restoration - Ontario Chapter’s Native Plan Resource Guide can be obtained by visiting their website: www.serontario.org
The North American Native Plant Society also has an excellent site with a Canadian section for northern gardeners. www.nanps.org.
The Ontario Invasive Plant Council has information about all aspects of invasive plants. http://www.ontarioinvasiveplants.ca/