In the Southwest part of the State, with a warm microclimate, you might even be able to grow some of the cold-hardy varieties of banana.

Or you could try growing Satsuma mandarins, though the flavor might not develop very well in that climate (the fruit develops best flavor when conditions are sunny and dry).

What about citrus: kumquat, mandarin, citrumelo? Warm microclimate in zone 8 might be equivalent to zone 9, so should be possible...

or cold-hardy varieties of pomegranate

Apricots are wonderful, of course, but I wouldn't waste your limited microclimate space planting an apricot tree there. There are plenty of cold-hardy apricot varieties that would do just fine where you are (I mean as far as temperature goes, those wet conditions are a different matter).

I like the idea of peach/nectarine. They should be self fruitful and would greatly benefit from being protected from wet leaves on the foliage in the spring. Its the wet leaves that make leaf curl a problem in the NW.

It may be more difficult to keep healthy and productive and controlled via pruning though.

Awesome, thanks everyone!

Fruitnut, I was hoping you'd answer!

What sort of pollination do the pluots need and what is your opinion on the other hybrids like plumcots and apriums?

The two pluots mentioned would benefit from having Flavor Grenade for pollination. It's well worth growing on it's own.

I've tried all the new complex hybrids and many apriums. None are better than the straight apricots mentioned. Some like Bella Gold peacotum were a total bust, poor set and inferior fruit.

I would also suggest posting this in the Northwest Gardening forum as well. I guarantee you will get some very different input from folks who actually live and grow fruits in the PNW. It's not as simple as just an assumption of a 'warmer microclimate' - I live in a warmer microclimate in the PNW - it is the amount of heat available that will cause these types of stone fruits to ripen properly. And that is unlikely to be present on any sort of reliable basis. And any citrus you would want to eat is out - there is nowhere in the PNW that remains warm enough to grow citrus or avocado outdoors. In containers, yes, as long as they are brought in for the winter.

btw, hardy bananas grow all over the place here and sometimes fruit (although not particularly edible or tasty) so a specialized microclimate is not really necessary for them. They still need to be heavily mulched and protected in winter, though.

Thanks gardengal48. I get what you're saying about heat units. Pushing the boundary is part of the fun

The climate zone in SW WA is 8b-8a, meaning the winter temperatures can get down to 10-20 degrees. Satsuma is one of the few more cold-hardy varieties of citrus, in fact in Japan they classify it in a semi-separate category from mandarins. That is why I mentioned it. (and more importantly it is really the only cold-hardy variety that tastes good)

I generally agree with what gardengal said. However, it is young bananas and citrus that are vulnerable to winter cold. Once they have a few years to become established they are much more hardy. I really think you might be able to grow [certain types of] bananas and citrus in a warm microclimate in SW WA without winter mulching. Just keep them in large pots the first few years so you can bring them inside and protect them until they have a chance to grow bigger. Yes, this is really pushing it, because citrus and bananas are not known to grow in WA, but I think it is possible.

I know the OP has not expressed interest in growing bananas, but just thought I would mention here that one of the rarer cold-tolerant varieties is Musa sikkimensis (known as the Darjeeling banana). Not the best tasting variety, but it would grow fine in the western side of WA.

Parker,

Sorry for appearing to mimic your words above, I was reading on my phone and for some reason could only see the part about the banana...

Of course I totally agree with you about the citrus, but I get the impression that there are actually a number of people growing citrus in the PNW, especially things like Yuzu.

Gardengal:

...and anyone who discounts citrus outside of really mild climates, should look up Stan McKenzie. He grows not just a single citrus tree in a favored warm microclimate of his house, but an entire small scale commercial citrus orchard (mostly mandarins, but a bit of everything) in Zone 8a, well inland South Carolina!