I bought two Elephant Ear bulbs that were labeled 'Elephant Ear Mammoth' from Wal-Mart. The bulbs are round and about 3 to 4 inches wide. Does anybody know the exact scientific name of this? I think it might be Colocasia esculenta but I'm not sure. I'm in zone 7a but many winters here are only 7b temperatures. Can I leave the bulbs in the ground all year here??? What is the best way to plant this Elephant Ear Plant having a heavy silty clay soil at my location? Thanks.