I have newly planted rhizomes dug up over and over no matter where I plant them. The critter responsible is not looking for the plant but what is in the soil it is planted in. So, I expect it is some nocturnal animal looking for grubs. Big established pots of any plants will be knocked over and the soil under the pot disturbed. Ground cover will have trails of 'ditches' in it as they search for their prey. Newly dug earth is a great place for grubs to migrate to apparently and since it is not packed soil it is the best place for the foraging animal to 'hunt'. Some of the irises are a ways away from the original planted area. Don't know what that is about but the rhizome is never eaten..... just discarded. I have to check on newly planted irises each morning during the hot months in order to keep a rhizome from lying in the sun and perhaps not surviving the ordeal.
