Autumn leaf color is a phenomenon that affects the normally green leaves of many deciduous trees and shrubs by which they take on, during a few weeks in the autumn season, one or many colors that range from red to yellow. The phenomenon is commonly called fall colors and autumn colors, while the expression fall foliage usually connotes the viewing of a tree or forest whose leaves have undergone the change. In some areas of Canada and the United States, "leaf peeping" tourism is a major contribution to economic activity. This tourist activity occurs between the beginning of color changes and the onset of leaf fall.
The Canadian countryside, except for the prairies and some tundra regions, is heavily forested with deciduous trees ie. they loose their leaves in winter. The leaves start the die-back process at the end of summer, and during the following fall (autumn) the dying leaves change colour.
It is forests full of these changing colours that create a visual spectacle on such a scale that people travel long distances to witness it.
There are different tree species across the country, so naturally the fall displays vary both in colours and timing. The intensity of autumn color is at its best in the eastern provinces although the western provinces of Alberta and British Columbia also have something to offer.
However, if the purpose of your visit is to see the very best of the fall foliage, then Ontario, Quebec or the eastern Maritime provinces would be the better choices. The Ontario Parks Dept lists no less than 50 viewing sites throughout the province!