Idun and the Apples, illustration from 'Teutonic Myths and Legends' by Donald A. Makenzie, Idunn/Iðunn - In Norse mythology the keeper of the apples of youth, she is known only through the myth “Idunn and the Golden Apples”
"she was a healer and enchantress, eldest of nine sisters. In early chivalric romances by Chrétien de Troyes, she also figures as a healer. Her character may be partially derived from that of the Welsh goddess Modron and other myths.
Trees in Celtic Mythology: Trees were hugely significant to the ancient Celts. They believed different kinds of trees served different mystical purposes that helped them through their lives. Possible wood hardness chart?