Does anyone have any experience planting this calla extra deep to avoid digging in winter in zone 6b? I would cover with mulch as well, but the ground doesn't freeze very deep here, maybe 6-8 inches. So I'm thinking of planting Zantedeschia aethiopica about 10 inches deep, and mulching to try an experiment to see if they survive winter. Being strong (and tall) growers, I'm just wondering about this.