Native Plant Guides for Willamette Valley Species
Wildflowers of the Pacific Northwest (2006, reprinted 2014)
by Mark Turner and Phyllis Gustafson
Timber Press Field Guide
Very basic key with photos, limited number of plants covered. More up-to-date than other definitive guides.
Mountain Plants of the Pacific Northwest (1995)
by Taylor and Douglas
Not a definitive key to Identifying species. Covers ferns, conifers, hardwoods, shrubs, forbs, grasses.
Plants of the Pacific Northwest (1994, revised edition 2004)
by Pojar and Mackinnon
Useful features, and interesting notes about the plants covered, but not sufficient for definitively identifying species. Covers 800 species found from the coast to the western Cascades.
Flora of the Pacific Northwest (1973)
by Hitchcock and Cronquist
Classic, authoritative guide, key, and portable plant ID manual. Still widely used, but now outdated, as the nomenclature and distribution of genera have changed. Covers nothing south of Eugene.
Update in progress, see http://www.pnwherbaria.org/florapnw.php
Plants of Western Oregon, Washington, and British Columbia (2005)
by Eugene Kozloff
Timber Press
Good resource, but not comprehensive.
The Jepson Manual of Vascular Plants of California (Second print edition 2012)
Also available online: taxa of all native and naturalized plant species found in California, by region
Univ. of CA at Berkeley
http://ucjeps.berkeley.edu/eflora/
Many of the same plants are also found in Oregon. This resource does not provide Oregon-specific information, but it does help with keying and identifying species.
Flora of Oregon: Pteridophytes (ferns), Gymnosperms (conifers), Monocots (lilies, irises, camas, etc.)
Vol. 1 (Sept. 2015)
Editors: Stephen C. Meyers, Thea Jaster, Katie E. Mitchell, Linda K. Hardison
Descriptions of over 1,000 taxa. Vols. 2 and 3 will cover dicots. Work in progress.
Taxa list of all plants included in each volume is available online at: http://www.oregonflora.org/flora.php#volumes
To purchase: http://shop.brit.org/products/floraoforegon1
Many other resources available online at the Oregon Flora Project website, including online geographic atlas, gallery of plant photos, flora checklist, rare plant guide.
The Butterflies of Cascadia
A Field Guide to All the Species of Washington, Oregon, and Surrounding Territories (2002)
by R. Michael Pyle