I have not seen any Brugmansia that have survived PNW winters without being brought in. However, I do have anecdotal evidence that it might be possible, even if extremely marginal.
For one, I left out my yellow flowering Brugmansia (probably Brugmansia suaveolens) during that brief snow we got last winter. Note that it didn't stay outside the entire winter, but I left it out some nights after watering. It died back to the base, however the roots survived. I up-potted it in the spring, applied fertilizer and put it in a greenhouse, where it will stay this winter. It grew about six feet, responding well to heat, ample moisture and fertilizer. See the photo below!
Lance Wright (@gardenriots) mentions growing Brugmansia sanguinea, although he doesn't say if he leaves it out over the winter. Apparently it is hardy to zone 9a, so it could work as a marginal perennial for most of Portland. However, it is unclear if the growers are referring to the ease of overwintering it in a particular zone or its actual cold hardiness. For example, Missouri Botanical Garden rates Brugmansia suaveolens at zones 8-10, while Cal Poly rates the same species at zones 10-12.
According to University of Washington, "Some Brugmansias will overwinter in the Seattle area and are semi-evergreen or evergreen. Others may die back to the ground and come back in the spring." This is plausible given some of Seattle's very mild microclimates that might not exist in Portland. However, I have yet to see any examples myself.
Thanks for inspiring this rabbit hole to go down!
John
Sources
I will add in a few days. The website won't let me right now.
