If you can keep escallonias through multiple winters there should be mild enough for outer coastal native Myrica californica. Grows right behind the dunes in nature.

I can't remember, are you out there by Tofino? Seems like you might have said that once. If so I'd consider species of Olearia such as O. macrodonta and O. traversii. And Pittosporum tenuifolium. Ian

Thanks for the replies guys. A horiculturalist friend turned me on to myrica californica when we first moved here, a rural area between Tofino and Ucluelet, that is correct. Good memory Ian! Supposedly this is the farthest north it is found in the wild. It would be a good choice, but I appreciate it more in its' natural shape or as an informal hedge, and have already planted a few specimens on the perimeter. O. macrodonta sounds interesting. Not sure I want to experiment with the hardiness of a hedge though, knowing what I know now.
I really love the form and colour of Chamaecyparis lawsoniana 'Elwoodii' but I understand it is subject to a lethal fungus in the PNW. Is that the case everwhere? How about the classic Yew? How would it take the wind? Thanks again for the assistance.

There is a wide range of Lawson cypress cultivars available, many more interesting and recent than that one. But as a rule all are prone to root rot, some apparently resistant seedlings having been identified only just recently - after much testing. If scanning around for a variety of planting possibilities maybe have a look at the plant selection guide portion of the Sunset Western Garden Book.

I tried Olearia macrodonta north of Seattle once and it froze right off after a year or so. If it really is significantly milder where you are, then maybe it would work. A site either never gets below the critical minimum temperature for a particular plant - or it does. It only takes a few hours. For the most part the only older olearias I see down here are scattered lingering specimens of O. x haastii remaining from public plantings in Seattle.

The Lawson cypresses at the link below designated The Guardian Series are supposed to be able to evade root rot. Note also that the cultivar offered as 'Golden King' (a hard-to-grow European cultivar from the 1950's) is actually 'Golden Showers', perhaps first listed (and maybe even originated by) Mitsch nursery in Oregon during 1976.

Here is a link that might be useful: Monrovia Plant Catalog

An acquaintance of mine in Tofino says the coldest temperature he recorded last December was -3.5C.... or about 26F. Not really cold enough to kill much of anything I like to grow. Historical data suggest much colder temperatures are possible there (at the Tofino airport anyways) but I just thought that was interesting.