Print-based:

[1] Trees in Canada,John Laird Farrar.

This book focus on the trees in Canada. It is really helpful if you want to find native plants to use in your design. Besides the habit, identification, and other basic information like this. The book also includes the maps of the trees ranges.

What is more, it divides the plants into different groups by the similar distinguished features. In this way, one can easily compare the trees with similar features.

Digital

[1] http://www.hort.uconn.edu/plants/detail.php?pid=141

This website is really clean and simple. No lengthy narration. Just shows all the information that are most important. So you can easily find what you want.

Besides, the selection of the photos are good. Fully shows the feature of the plant.

[2] http://www.pfaf.org/user/Plant.aspx?LatinName=Salix+scouleriana

On this website you can find most on the information you want. But what I like most about this website is that it will introduce other uses of a plant. Not only the ornamental value but also he edible uses and medicinal uses.

What is more you can download the information as a pdf. It is so convenient.