Gernumbli

• Type: Magical Creature
• Ministry of Magic Classification: XX (Harmless / may be domesticated) (Fantastic Beasts and Where to Find Them)
• Native To: Europe and North America (Fantastic Beasts and Where to Find Them)
• Distinguishing Features: Fleshy, spineless, tentacled fungus-like appearance; secretes a destructive slime (Fantastic Beasts and Where to Find Them)

The Gernumbli is a magical pest that infests Wizarding gardens. It appears as a fleshy and spineless creature, strongly resembling a tentacled fungus. Its primary diet consists of the roots of magical and mundane plants. A key characteristic of the Gernumbli is the trail of thick slime it secretes. This slime is highly destructive to vegetation, causing it to rot and blight. The creature is known to be particularly fond of Gillyweed, making its cultivation a challenge in infested areas. The most effective methods for controlling a Gernumbli population are introducing its natural predator, the Gnome, into the garden, or by using a specially prepared substance known as Gernumbli Blight.

The Gernumbli holds a role in the wizarding world analogous to that of a slug or snail in the Muggle world—a common and irritating garden pest that must be managed to protect cultivated plants. Its existence is well-documented in magizoological literature, most notably in Fantastic Beasts and Where to Find Them by Newt Scamander, which serves as the primary source of information on the creature. The Gernumbli is not mentioned within the narrative of the original seven Harry Potter novels.

• The Gernumbli was created by J.K. Rowling for the supplementary textbook Fantastic Beasts and Where to Find Them, which was first published in 2001 to raise money for the charity Comic Relief.
• A visual depiction of the Gernumbli appears in the video game Hogwarts Legacy. In the game, they are found in greenhouses and can be collected as an ingredient for potion-making. (video game)