My son-in-law went out to harvest the rutabagas yesterday and when he dug them up there was just a purplish white root that smelled like a rutabaga but no rutabaga! The leaves that were above the ground were big and full and green. We thought we would go for one to see if they were ready yet and just found this root. These roots were about 6 inches long and kinda skinny. So, we tried another and --- same thing --- just a purplish root. We planted them in May. We are in the south suburbs of Chicago which I think is zone 4 or 5. Can anyone tell me what we did wrong?