We are currently enjoying the Celtic Month of the Elder.
'The unique personality of the elder was anciently believed to come from the spirit of the 'Elder Mother' who dwelt within the tree. The Elder Mother, called Elle or Hyldemoer in Scandinavian and Danish myth, worked strong earth magic and according to legend, avenged all who harmed her host trees. No forester of old would touch elder, let alone cut it, before asking the Elder Mother's permission three times over and even then he was still in dread of her possible wrath. Likewise, in many country districts of Europe and Britain, wise people still show respect by touching their hats when passing elder trees, in continuance of ancient custom. Certain North American tribes also believe that elder is the Mother of the human race.
According to legend, witches would often turn themselves into elder trees, and one famous witch-tree turned a king and his men to stone, thereby creating the Rollright Stones in Oxfordshire. This ancient piece of folklore tells of a Danish King, on his way to battle for the English Crown with his warriors, meeting the witch and asking her what his fate would be. The witch replied:
Seven long strides thou shalst take,
And if Long Compton thou canst see
King of England thou shalst be.
Because he was almost at the crest of a hill, the Dane was confident as he strode forth, but unexpectedly at his seventh stride a long mound rose up before him, blocking his view.
The witch replied:
As Long Compton thou canst not see,
King of England thou shalst not be.
Rise up stick and stand still stone,
For King of England thou shalst be none,
Thou and they men hoar stones shall be,
And I myself an Elder tree.
In an instant the Danish King and his men were turned to stone. Those warriors loyal to the King became the King's Men stones set in a circle; and those who had questioned his authority turned into the Whispering Knights, huddled together and apart from the others. The King himself became the King Stone, standing, still in shocked attitude, apart from all his men. The witch then resumed her guise as the guardian Elder tree.'
from 'Tree Wisdom' by Jacqueline Memory Paterson.
Following picture from Wikipaedia: The Rollright Stones of Oxfordshire.