This article is about the tree. For the chapter, see The Whomping Willow
From the Story
Discovered in Book 2, Chapter 5, The Whomping Willow
"The Whomping Willow is a tree that stands on the Hogwarts grounds and uses its branches to hit and smash whatever it comes into contact with. Ron and Harry crash into the Whomping Willow when they drive the flying Ford Anglia onto school property. The tree pummels the car until it reverses out of reach of the tree's branches."
Discovered in Book 3, Chapter 17, Cat, Rat and Dog
"The Whomping Willow attacks Hermione and Harry as they stand at the base of the tree, stopping them from getting close to the roots. Its branches hit Harry across the face, and Hermione across the shoulder. The movements of the tree only stop when Crookshanks presses a knot on its trunk. It freezes in place as though made of marble. There is a large gap in the roots of the Whomping Willow, the entrance to a tunnel."
Discovered in Book 3, Chapter 18, Moony, Wormtail, Padfoot and Prongs
"Remus Lupin tells Harry that the Whomping Willow was planted the year that he, Sirius Black, James Potter and Peter Pettigrew started at Hogwarts. It was planted to cover the mouth of a tunnel built for Lupin's use during the full moon, to stop anyone from coming across Lupin whilst he was dangerous."