Zantedeschia aethiopica - the pure white tall calla lily - is quite hardy....easily to zone 7, probably to zone 6. It is the smaller hybrids, often colored or with patterned/spotted leaves, that are not hardy in most climates.

The tender forms of Zantedeschia are mainly hybrid cultivars of Z. elliotiana and Z. rehmannii but may also include Z. albomaculata and Z. jucunda. These are typically referred to as Zantedeschia x hybrida.