Oregon grape (Mahonia aquifolium) It is not uniquely resident to here or even to what was once the Oregon Territory. It is, however, a useful and attractive shrub.
Blue elderberry (Sambucus cerulea) I like it's look but not many people make use of it in their yard. There are related species more commonly used for that purpose.
Serviceberry (Amelanchier alnifolia) They have just bloomed here. There is a Native American tribe in Oregon with a name used by others that translates "People of the Serviceberry."
Lewis mock-orange (Philadelphus lewisii) They will soon fill our air with their fragrance

. I don't know if they are a common landscape plant elsewhere. It seems like they should be.
Arrowleaf Balsamroot Sunflower (Balsamorhiza sagittata) just about symbolizes my local environment for the last 50 years. I like to refer to it just that way "Arrowleaf Balsamroot Sunflower." If the botanists would include the stem - we would have the entire plant description as parts of its name

. I doubt that very many people actively plant it in their yards.
Blanketflower (Gaillardia aristata) I understand that it now is considered an invasive in Europe. For some reason, that makes me smile but I know that those situations are not ideal. I guess it kind of comes down to keeping species that require human involvement to maintain the environment or maintaining a wild, native landscape.
Steve