As a tropical plant native to South America, angel trumpets can only survive the winter outdoors in areas south of the United States Department of Agriculture's hardiness Zone 9, which covers most of the American South and Southwest. In those zones, the plant requires no winterizing. In colder zones, the angel trumpet can only survive the winter by being brought indoors prior to the first frost.
For angel trumpets to survive the winter in colder areas of the country, the plants must be protected from frost damage by being brought indoors. Due to the reduced sunlight in winter, the plant should be placed in the area of the house that receives the most sun exposure, ideally a south-facing window. The angel trumpet should be placed on a porous surface that allows for adequate soil drainage and evaporation, which provides some necessary humidity for this moisture-loving plant.
Angel trumpets, especially in winter, dry out much more quickly due to the lower humidity in the air. Therefore, they require more frequent watering attention to remain healthy. Be wary of overwatering and overfeeding, as the plant is dormant during the winter and new growths should be discouraged, just as dead leaves should be trimmed. Keep the soil moist 3 inches below the surface, but not any deeper, to avoid over-saturating the soil. Try to keep the plant in an area where the temperature does not dip below 60 degrees Fahrenheit. Experts recommend placing the plant in a south-facing bathroom so that it may benefit from a bathroom's increased humidity.