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

Knotgrass was a plant with magical properties. It was used in potion-making, and was an essential ingredient in the making of the Polyjuice Potion,[4] as well as in the brewing of the alcoholic beverage Knotgrass Mead.[5]


The Daily Prophet reported in its 29 November 1926 issue that an unusually dry season had lead to a shortage of knotgrass.[6]

"Welcome back class! Today we will study Knotgrass. Knotgrass can be found growing in the Forbidden Forest. It's not grass. Sorry, I couldn't resist. Let's discuss the care and uses of Knotgrass."
Professor Sprout to sixth-year Herbology students[src]

Jacob's sibling having re-grown knotgrass with Herbivicius

During the 1989–1990 school year at Hogwarts School of Witchcraft and Wizardry, Professor Pomona Sprout taught sixth-year Herbology students about how to properly cultivate and handle knotgrass.[2] Later during this school year, Jacob's sibling took some knotgrass from the Herbology Classroom so they and their friends could brew Polyjuice Potion with it. In order to cover up them taking the plant, they rapidly grew some more knotgrass with the Herbivicus Charm so Professor Sprout would not be suspicious about its absence.[7]

Knotgrass could be found growing in the Forbidden Forest.[1][2] Harry Potter and Hermione Granger struggled through a patch of it on their way back from their first meeting with Grawp in 1996, just before they and Hagrid were approached by the centaurs.[1]

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.[8]
  • The use of knotgrass in the Polyjuice Potion was chosen by J. K. Rowling to represent "being tied to another person".[9]
  • In the GBA version of Chamber of Secrets, this is instead received from a Venomous Tentacula.


Notes and references

  1. 1.0 1.1 1.2 Harry Potter and the Order of the Phoenix, Chapter 30 (Grawp)
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Harry Potter: Hogwarts Mystery, Year 6, Chapter 7 (Niffler Hunting) - Herbology Lesson "Knotgrass"
  3. 3.0 3.1 3.2 Pottermore
  4. 4.0 4.1 Harry Potter and the Chamber of Secrets, Chapter 10 (The Rogue Bludger)
  5. 5.0 5.1 Label Collection book included with the Harry Potter Wizard's Collection (see this image)
  6. Fantastic Beasts and Where to Find Them (film) (see this image)
  7. Harry Potter: Hogwarts Mystery, Year 6, Chapter 32 (Quest for Polyjuice)
  8. Maud Grieve, A Modern Herbal, Dover Publications (1976)
  9. Pottermore - The Polyjuice Potion - J.K. Rowling's Thoughts
Blossom Degrasse · Miranda Goshawk · Quiac Marinus · Beaumont Marjoribanks · Nepali wizard · Gethsemane Prickle · Sanjay Shanker · Selina Sapworthy · Phyllida Spore · Tilden Toots · Hadrian Whittle · Sir Winogrand
Herbology at Hogwarts
Herbology Award · Herbology Lesson Cup · Herbology Race Cup · Herbology Store
Greenhouses One · Two · Three · Four · Five · Six · Seven · Professor's Office
Professors Herbert Beery · Pomona Sprout · Neville Longbottom · Unnamed Professor (19th century)
Textbooks Flesh-Eating Trees of the World · Ingredient Encyclopedia · One Thousand Magical Herbs and Fungi · Winogrand's Wondrous Water Plants
Plants studied and grown at Hogwarts
Aconite · Alihotsy · Asphodel · Belladonna · Bouncing Bulb · Bubotuber · Bubotuber pus · Chinese Chomping Cabbage · Cowbane · Devil's Snare · Dirigible plum · Dittany · Fanged Geranium · Fat cactus-like plant · Fire seed bush · Flitterbloom · Floo · Flutterby bush · Fluxweed · Gillyweed · Ginger · Hemlock · Honking daffodil · Ivy · Knotgrass · Lady's Mantle · Lavender · Leaping Toadstool · Lovage · Mandrake · Mimbulus mimbletonia · Mistletoe · Moly · Nettle · Peppermint · Puffapod · Raspberry · Rose · Sage · Screechsnap · Scurvy grass · Self-fertilising shrub · Shrivelfig · Snargaluff · Sneezewort · Sopophorous plant · Sopophorous bean · Spiky Bush · Spiky Prickly Plant · Stinksap · Sugar Shrub · Toad-eating plant · Tormentil · Umbrella Flower · Valerian · Vampiric vegetation · Venomous Tentacula · Walking plant · Wax vegetables · Whomping Willow · Wiggentree · Wild rice · Wormwood
Spells taught in Herbology at Hogwarts
Fire-Making Spell (Incendio) · Herbivicus Charm (Herbivicus) · Incendio Duo Spell (Incendio Duo) · Lumos Solem Spell (Lumos Solem) · Severing Charm (Diffindo)