Rick I notice you're Koppen Zone is Mediterranean. Winters on the dry side? With mulch and plastic sounds like a plan. Like many Aroids I've observed it's the cold/wet combination that creates problems. In especially cool/wet autumn seasons I'll find some rotting tubers when I lift them. This is also the wisdom passed down to me from my folks, from whom many of my Calla were inherited.
My guess is cool storage is simply to prolong dormancy. What are you talking as a time frame, 2-3 months dormant? All but Z. aethiopica need a dormant period in order to bloom, (as far as I've read).
We regularly get below 0F. I'm going to try some A. konjac with mulch and plastic this winter.
