Well, let's not start off with the expectation of killing the plant. Brugmansias for the most part are tropical, However, there are Brugmansias that thrive in colder climates. You will just have to get used to cutting them back and storing them in the house until the frost comes. That is a good time to drench them as well with Forbid to kill any spider mites that may live in the soil. I would remove enough soil to fit in a 2-gallon pot. Come spring, move the plant into a 5-gallon pot after it has gotten about 2 weeks of outside sun. Don't want to put it into shock but moving it too quickly to the larger pot.
sorry... I had to look these up (PNW is an acronym for Pacific Northwest, which includes Oregon, Washington, Idaho, and British Columbia in Canada. Some consider parts of California, Montana, and southeastern Alaska part of the Pacific Northwest, too)
