Hi Denys, While N. bowdenii is hardy here in Z7/6, I doubt it will like Z4 conditions. In its native habitat it would be fairly dry and cold in winter, though here in the NYC area it is anything but dry in winter. Probably best to bring your pot indoors when the leaves yellow (or when really hard frosts threaten) and keep in a cool/cold area and rather dry for winter. Incidentally the flowers come so late that they can get nipped by frost, so keeping it a pot that can be moved indoors can be an advantage. Ernie DeMarie Briarcliff Manor, NY Z6/7