This checklist is based upon Hitchcock & Cronquist's Flora of the Pacific Northwest, 2nd Edition. The extent of the "Pacific Northwest" as defined in this flora is a bit different that used in most non-botanical contexts: FPNW's boundary excludes the southern parts of Oregon and Idaho, and extends eastward through the westernmost part of Montana. To the north, British Columbia is included as far as 51°N.

For more detailed information, see the "Flora Region Boundary" page on the Flora of the Pacific Northwest site.