Leek jinx

Warning!

At least some content in this article is derived from information featured in Harry Potter: Hogwarts Mystery. Spoilers will be present within the article.

"A number of small scuffles broke out in the corridors, culminating in a nasty incident in which a Gryffindor fourth-year and a Slytherin sixth-year ended up in the hospital wing with leeks sprouting out of their ears."

—Description^[src]

The Leek jinx (incantation unknown) was a jinx that could be used to make leeks sprout from the victim's ears.^[1]

History

In June of 1994, a series of nasty incidents in the prelude to the Gryffindor-Slytherin Quidditch match in the finale of the Inter-House Quidditch Cup ended abruptly with the use of this spell on a Gryffindor fourth year and a Slytherin sixth year; this necessitated their visitation of the Hospital Wing.^[1]

Behind the scenes

It is never stated that the leeks were conjured by the spell; they could have been induced by magic or non-magically forced into the victims' ears, although the use of a jinx or hex is the most likely cause of the phenomenon.
In Harry Potter: Hogwarts Mystery, this is an award-only spell that can be used in duelling using Sneaky stance. It deals moderate damage and can stun opponents in a defensive stance for 1 turn. The spell is awarded by defeating 20 duellists in 2 days when the Duelling Club is first discovered after duelling and defeating Merula Snyde.