I agree with Ellen - many Callas are hardier than we think - I have seen a plant that closely resembles Z.albomaculata (either a hybrid or selection of the species) practically becoming invasive planted near the foundations of houses in both New Jersey and Rhode Island. Although the house does provide a winter buffer with the quantity of plants that were there they have been growing for quite a while. I am sure that over time the tubers have also migrated deep into the soil. Marc NJ USA