Alexander, welcome to the Citrus Grower Forum, thank you for joining, we are very happy to have you as a member. In zone 7B you could grow Trifoliate orange, Ichang Papeda (Citrus ichangensis) in the ground, these are hardy to about -26C.. With protection at extremely cold times, you could grow Citrandarins (Poncirus X Mandarin), Citranges (Poncirus X Oranges), Citrumelos (Poncirus X grapefruit) all of which are hardy to about -15C.. - Millet