Calla lilies overwintering in Ohio...
I'm not too familiar with these plants, meaning, I do know what they are but have never grown them, either here in MD or when I lived in Ohio.
However, my father has several cultivars of Zantedeschia that have overwintered and returned every year for a decade, with nothing more than being 2 feet from the foundation and a few inches of shredded wood mulch. Not "extra" mulch, just the mulch that's already in the planting bed that he replenishes from time to time.
This is in NE Ohio...zone 5b/6a depending on the map you use. Does this seem contrary to popular opinion?
Although I'd be curious to see if they return THIS spring.