Some of the older traditional ballads involve the central character answering difficult or seemingly impossible questions. Naturally, as in this song, the pure heart and motives of the rescuer are stronger than the evil enchantment. In the 1960s there were several versions of this song going round the folk clubs in Hertfordshire.
The oldest mulberry tree in Britain is in Spitalfields, London. The Gentle Author will tell you more at http://spitalfieldslife.com/2015/05/05/the-oldest-mulberry-in-britain/