It is a big (+-4ft) single plant already. Will do as you say and dig it to re-plant in a sunnier location by itself. Will post pics once this is done. It should have a lot of tubers because of its age. Am guessing that the sport is only on the main stalk though and wouldn't come from the attached tubers? Could the big Manihot grahami overgrowing the group of yuccas cause the mutation?