Gardenway has over 45,000 plants in their data base.
Great Plant Picks (GPP) is an educational program of the Elisabeth C. Miller Botanical Garden which debuted in 2001 with the first recommendations for a comprehensive palette of outstanding plants for the maritime Pacific Northwest. To date over 900 exceptional plants have been selected for gardeners living west of the Cascade Mountains from Eugene, Oregon, USA to Vancouver, British Columbia, Canada.
Hansen’s Northwest Native Plant Database – a comprehensive list of native plants with descriptions and photos.
How to Identify Rhododendron and Azalea Problems a Washington State University Extension Bulletin
Native Plant Guide from King County, Washington State
Oregon State University Landscape Plants Images, Identification and Information – This site contains images and information on over 1,700 landscape plants (mostly woody) listed in alphabetical order by genus.
Pacific Horticulture has articles focusing on plants, gardens, design, and concern for the environment
Plants for a future is a database where you can search for over 7000 edible and medicinal plants using a number of search criteria
The Plant List has a working list of all known plant species.
UBC Botanical Garden Forums – plant identification
Vancouver Hardy Plant Group – dedicated to the Cultivation and Study of Hardy Herbaceous Perennials