When you make a commitment to eat local food, you're going to have to accept that certain foods will no longer be available to you. The reason for this is that the types of plants that thrive in your area are not the same types of plants that thrive elsewhere. Each plant has its own hardiness zone which determines where it can be grown without the aid of artificial climate control (i.e. a greenhouse). This article can help you figure out what you can grow.
When scientists are determining which zone your area fits into, they look at the average temperatures for that area as well as the lowest temperatures reached in the winter in degrees Celsius. Zones go from 1 (-51) to 11 (+10) and are given a or b subcategories depending on the temperature range they experience during a year. This system was developed by the US Department of Agriculture and is used internationally to label plants and identify the different climate zones.
Though the hardiness zones are useful in determining which types of plants you should buy, they are not perfect. They do not take into account the maximum summer temperature, the reliability of snow cover, soil moisture, humidity, or the risk of frost. Therefore many gardening magazines advise you to combine hardiness zone information with additional information, such as heat zones, though most gardeners opt to use trial and error starting with certain indicator plants which are representative of each zone.
To find out what zone your home is located in, you can check out the free maps available online through the USDA and Agriculture and Agri-Food Canada. Much of southern Ontario belongs to the 6a zone while the interior is rated 5a. Most of Canada's North is rated 0, which means nothing will grow there. With the United States, there are 11 different zones arranged roughly in stripes with the hottest near the Mexican border, however Sunset Magazine has a more finely graded 45 zone map for gardeners.
Once you find out your hardiness zone, you need to set about choosing plants that suit it for the gardens of your property. Check plant packaging for information on its hardiness, which will usually be given as a bracket (i.e. suitable for zones 4 through 8b) or as a maximum (hardy to zone 10). Your local gardening store should focus on plants and seeds suitable to the local climate, but if you're unsure whether a plant is suitable as an employee for advice or consult with your local gardening co-op or club. Gardeners are always happy to share tips.