My calla lilly did not bloom last year and I read up on the plant and the instructions say to plant in 4 inches of soil. Does that mean the hole is 4 inches deep regardless of the size of the rhizome or put 4 inches of soil over the rhizome?
I noticed with my calla lilies that when they die back in the winter this leaves a nice hole in the ground were slugs love to hind and munch on the new shoots that emerge in the spring. When I remember I fill this in with soil shortly after they die back. As for your question they probably mean that you should leave enough depth in the hole for 4" of soil on top of the rhizome and loosen the soil around it about the width of a shovel.
