Don, here on the south west coast of Canada, just like Seattle and similar to Portland, we are a mild zone 8 climate generally speaking not too cold - maybe - just maybe a night or 3 at the bottom of the zone 8, perhaps 7 to 10 days where the temperature stays below freezing through the day and another 10 - 14 nights of hard frosts. where temperatures drop below freezing - 31f to 20f.
So the winter is not much of an issue. With a little tlc citrus can be grown outside.
The bigger issue is lack of heat - our spring may be late arriving and our summers my be short lived and cool.( homes with AC are rare) In most cases, but not all, it is best to grow citrus up against a south facing wall(full sun) and under a clear overhang or in a cold frame.If not, a late bloom and late growth and lack of fruit will be the result. Also, speaking to a local 'citrus pioneer', he grows most all of his citrus in a large hoop style cold frame. Acidic citrus such as Bearss limes and Meyer lemons and perhaps sudachi do better because prolonged heat is not required to ripen the fruit. For other varieties like satsumas,Oroblancos,trovita orange, He finds leaving the apparent fully developed fruit on the tree till spring actually produces a sweeter fruit than one harvested in the late fall.
I don't know if this will help in your Wikipedia post or not. If you want to know more about my hardy citrus experiences send me a PM. I am in my 3rd year of experimentation - by all accounts a NEWBY.
Cheers, Greg
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Gregn, citrus enthusiast. North Vancouver Canada. USDA zone 8. I grow In-ground citrus, Palms and bananas. Also have container citrus