If you are curious about the plants you see while walking and hiking through Washington’s urban and natural areas then the Washington Native Plant Society shares your interest. They have 12 chapters located throughout the state to choose from. Check out their website and see what they have to offer.
Publications include the quarterly journal, Douglasia, Occasional Papers and Local Chapter Newsletters.
The state flower of Washington is the Coast Rhododendron, Rhododendron macrophyllum. A broadleaf evergreen native to western North America and discovered by Archibald Menzies in 1792.
Field Guide to the Rare Plants of Washington by 
Gardening with Native Plants of the Pacific Northwest by 
Archibald Menzies, 1754-1842, was a Scottish surgeon, botanist and naturalist. He accompanied Captain George Vancouver on the HMS Discovery for the exploration of the west coast of North America. Menzies' name is commemorated in the scientific names of several of the plants he discovered, including Menziesia, a genus of shrubs in the Ericaceae, and the Douglas-fir, Pseudotsuga menziesii, one of the most significant trees in western North America. Menziesia was a genus of flowering plant in the family Ericaceae. More recently it has been reclassified within the genus Rhododendron. Archibald Menzies found this shrub in 1792 when he and George Vancouver landed near present day Port Discovery.