- "Harry's heart gave a huge leap every time he saw the word 'water' on a page, but more often than not it was merely 'Take two pints of water, half a pound of shredded mandrake leaves, and a newt...'"
- —Harry searches for references to water, hoping for help on the Second Task of the Triwizard Tournament[src]
The leaves of a mandrake can be used as ingredients in Potions. They also have additional magical properties: part of the process by which one becomes an Animagus is holding the leaf of a mandrake in their mouth for an entire month.
In 1995, while searching for information that would help him survive the Second Task of the Triwizard Tournament, Harry Potter searched books feverishly for references to "water," but generally found unhelpful information such as Potions suggestions that mentioned water, along with other ingredients such as mandrake leaves.