Jim, my observations won't be of any substantial help for you, being me in zone 9, but I have Haemanthus coccineus in the ground from years and they haven't got any damage with lows of -3°C (26-27F) several nights. Consider that leaves are just flattened on the ground and there it could have been even lower. Albiflos is less hardy in my opinion or maybe leaves get scorched from winter sun too. Plants of this species under canopy plants are instead very healthy. best regards Angelo Porcelli south of Italy