Daturas are treated as annuals because they are! But like some other true annuals they can be coddled into staying alive over winter but most who have tried this report less than optimum growth or flowering the second season. It may be good to try them from seed as a backup, just in case. OTOH, brugmansias are woody tropical shrubs and can be overwintered quite well, either as a houseplant (often are plagued by spider mites in this situation), forced into dormancy and kept in a cool dark location, or by taking cuttings, which root very easily.

I have a Datura I kept in my cold but non-freezing garage one winter. It bloomed the next year. Last winter I planted it in the ground to see what would happen. I thought it didn't make it but in late summer a shoot came up, but it only got 9" tall and didn't bloom, so it did better the first winter. I haven't grown them from seed.

I have had good success overwintering datura in the ground and in the garage. The root is like a big white carrot storing carbohydrates. The top dies back and a rough callous forms on stub. As it warms up in the spring the callous erupts into multiple new sprouts.

If you give it lots of hot sun it will come back much bigger the second year. I had one in Tacoma that got huge the second year and had 20 new flowers every evening in the warmest part of July/August.

Yours in the pot will do fine in an unheated garage. Don't let it freeze, and treat it like a potato in storage--dark, cool, humid but no watering. Watch for the new growth in March/April. You can give it a jump start in a warm south window or a greenhouse before putting back outside.

Best Luck,

Jim