"This is the most complicated potion I've ever seen. Lacewing flies, leeches, fluxweed, and knotgrass. Well, they're easy enough."
Hermione Granger on the Polyjuice Potion ingredients[src]

Knotgrass is a plant with magical properties. It is used in Potion-making, and is an essential ingredient in the making of the Polyjuice Potion,[1] as well as in the brewing of the alcoholic beverage Knotgrass Mead.[2]

The Daily Prophet reported in its 29 November 1926 issue that an unusually dry season had lead to a shortage of knotgrass.[3]

Knotgrass can be found growing in the Forbidden Forest.[4] Harry Potter and Hermione Granger struggled through a patch of it on their way back from their first meeting with Grawp, just before they and Hagrid were approached by the centaurs.[4]

Behind the scenes

  • Knotgrass may refer to several species of the Polygonum genus found in England and Europe. It is most likely Polygonum aviculare, which was believed to halt the growth of animals, and was mentioned as such in the works of William Shakespeare.[5]
  • The use of knotgrass in the Polyjuice Potion was chosen by J. K. Rowling to represent "being tied to another person".[6]
  • In the GBA version of Chamber of Secrets, this is instead received from a Venomous Tentacula.


Notes and references

  1. Harry Potter and the Chamber of Secrets, Chapter 10 (The Rogue Bludger)
  2. Label Collection book included with the Harry Potter Wizard's Collection (see this image)
  3. Fantastic Beasts and Where to Find Them (film) (see this image)
  4. 4.0 4.1 Harry Potter and the Order of the Phoenix, Chapter 30 (Grawp)
  5. Maud Grieve, A Modern Herbal, Dover Publications (1976)
  6. Pottermore - The Polyjuice Potion - J.K. Rowling's Thoughts
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