Gillyweed

Gillyweed is a magical plant native to the Mediterranean and resembling a bundle of slimy, grey-green rat tails. When it is eaten by a witch or wizard, one grows gills and webbing between the fingers and toes. There is some debate among Herbologists as to the duration of the effects of Gillyweed on fresh water versus salt water, but the effects of Gillyweed in fresh water seems to last about an hour.

Gillyweed can also, presumably, be used as an ingredient in a drink called Gillywater. Professor McGonagall once ordered a glass of it in The Three Broomsticks. Romilda Vane offered Harry a glass of gillywater spiked with a love potion in an attempt to get Harry to ask her to Professor Slughorn's Christmas Party.

Harry Potter used Gillyweed during the Second Task of the 1994 Triwizard Tournament. Dobby the House Elf gave it to him, under the direction of Barty Crouch Jr. who was disguised as Professor Moody.

Behind the scenes

 * Chocolate Frog Cards reveal that Gillyweed's properties were first discovered by Elladora Ketteridge but credited to Beaumont Marjoribanks about a century later.
 * Gillyweed is featured in Magical Water Plants of the Mediterranean and Magical Water Plants of the Highland Lochs, books lent to Neville Longbottom by Barty Crouch Jr., who was posing as Alastor Moody.
 * In the film, Neville Longbottom tells Harry about Gillyweed (he learned of it in a book Moody had given him), and is given the actual Gillyweed by Longbottom and told to put it in his mouth by Crouch/Moody.
 * There seems to be some Gillyweed stored in the Herbology Greenhouses.

Appearances

 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Goblet of Fire (film)
 * Harry Potter and the Goblet of Fire (video game)
 * Harry Potter and the Order of the Phoenix (video game)

Notes and references
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