The Washington Native Plant Society is an excellent resource for learning about native plants. They organize field trips and study weekends, where you can learn to identify plants where they grow. You can learn more from the featured speakers at their monthly meetings and at the plant identification workshops which precede the meetings. The society offers a ten week plant stewardship program with speakers and field trips covering native plant identification and many other topics.

Their website has features that can help with plant identification:

• A photo gallery that has habitat information and bloom times as well as photos
• Plant lists for many of the trails in Washington and a comprehensive list for each county
• Information about using native plants in landscaping, including photos, plant descriptions, and information about habitat, growing the plants, ethnobotany, and wildlife

The Puget Sound Chapter in Seattle is the largest and most active chapter, but there are eleven other chapters in Washington.  Many other states have native plant societies.