A common tree with significance in many cultures & religions. Often personified. English folk tales uniquely portray them as evil & mobile.

Tales of sinister willows that could uproot themselves to find new places to perpetrate evil undoubtedly influenced Tolkien's writings. Especially Old Man Willow. Tolkien of course gave justification for the trees' anger and game them Treebeerd to be their contemplative representative, protector, and avenger.