Gardening in Ontario, Canada presents challenges because of the broad span of plant hardiness zones found within the province. For example southern and eastern Ontario, bordering on the Great Lakes, contain temperate growing zones from 3 to 6a. Toronto is zoned 4 and Ontario warms to 6a as it reaches Windsor, which is actually south of Detroit. Cold zones and shortened growing seasons are possible in eastern Ontario, but by and large occupy the rest of the province, going as low as zone 1. Learning about your zone and using the help of local organizations and nurseries will insure your garden's success.
To understand Ontario soils and growing conditions, it is useful to recognize the importance of dense forest throughout the province. Much of temperate Ontario falls within the boreal forest, and eastern/southern regions occupy the mixed-wood forest belt, with deciduous and evergreen trees. Soils tend toward acidity, especially in evergreen areas. The relatively narrow bands that denote hardiness zones in eastern Ontario suggest the importance of understanding local climate conditions and the necessity of taking a short-season approach to summer gardening, which may not get fully underway till late May.
Ontario is a heavily forested province. Cold-tolerant evergreens cover the bulk of the province. There are a dozen varieties of seedlings, including pines, balsam, cedar and other components of an active commercial lumbering industry. Deciduous trees found in the mixed-forest border that covers the southern and eastern portions of the province include varieties of maple, aspen, ash, beech and oak.
Plant World's list of native Ontario shrubs reads like an idealized walk through the woods: red-barked and gray dogwood, raspberries, currants, and lingonberries. A wide range of blooming, berry-bearing shrubs populate the undercanopy of mixed-wood forest and lend beauty to gardens and yards. Summersweet, honeysuckle and wild rose add fragrance to a broad spectrum of shrubs.
Tender Perennials and Annuals
While eastern Ontario soil is hospitable to many tender perennials and annuals, hardiness zones dictate relying on nurseries that focus on local conditions. Seeds of Diversity publishes a resource list for native and organic gardeners, listing everything from fruit trees to flowers. Many nurseries on this list note their location climatologically, as well as by address. Catalogs offer a huge range of open-pollinated seeds and plants, from hydrangeas, lilacs, and peonies to blackberries in plant form. Rosters of flower seeds and plants assure colorful yards filled with impatiens, dahlias, zinnias, gladiolus, and other classic summer flowers. Rose cultivation includes careful directions on measures needed to winter them over
Nurseries and seed companies offer a broad variety of choices for vegetable gardens, with particular emphasis on heirloom varieties with reputations for doing well locally and taking full advantage of short-season hybrids. Again, awareness of the cold predominates in seed lists. Hawthorne Nurseries stress that its seeds have all been acclimatized to their location in zone 5, while Holes targets its services to northern gardeners. Hope Seeds restricts its stock to zones 3, 4 and 5. Tomatoes, onions, greens are possible, so long as the gardener respects climate conditions.