There are four kinds of hydrangea varieties native to North America, but none of these actually grow wild in Canada. Representing some of the best flowering shrubs, the smooth or wild hydrangea (H. arborescens) grows from New York state south to Florida and Georgia. Oakleaf hydrangea (H. quercifolia) has a more limited distribution and grows from North Carolina south to Florida and Louisiana. These are widely seen in gardens, usually as one of their named varieties.
The ashy hydrangea (H. cinereal) is found wild from Illinois and Indiana south to Alabama and Georgia. Meanwhile, the silverleaf hydrangea (H. radiata) is found only in parts of the Carolinas, Tennessee and Georgia. These two are seen less often in gardens.