The Whomping Willow of the Hogwarts School of Witchcraft and Wizardry grounds is a very valuable, very violent tree which was planted in a solitary location on the school property. Whomping Willows attack anyone and anything that comes within range of its branches. There are two known ways to immobilize the particular Whomping Willow placed at Hogwarts: pressing a particular knot at the base of the tree or using the "Immobulus" spell.
