The Mimbulus mimbletonia is a very rare magical plant that resembles a small, grey cactus. Instead of spines, its surface is covered in boils, which are described as looking like small tumours. The overall appearance of the plant is said to be like that of a “badly squashed, diseased internal organ,” and it pulsates slowly. When prodded or handled, the Mimbulus mimbletonia is known to make odd, crooning noises.
The primary and most notable magical property of the Mimbulus mimbletonia is its unique and powerful defence mechanism. When it feels threatened or is provoked, the plant contracts and squirts a foul-smelling liquid from every one of its boils. This liquid, known as Stinksap, is thick, non-poisonous, and dark green. Its odour is described as smelling strongly of rancid manure. While the Stinksap is harmless, its powerful and unpleasant smell makes it an effective deterrent. The plant is highly valued by some wizards and witches with an interest in rare flora.
The Mimbulus mimbletonia owned by Neville Longbottom was discovered in Assyria by his Great Uncle, Algie Longbottom. Great Uncle Algie gave the plant to Neville as a fifteenth birthday present in the summer of 1995. Neville was extremely proud of his new possession and brought it with him to Hogwarts School of Witchcraft and Wizardry aboard the Hogwarts Express at the start of the school year.
The Mimbulus mimbletonia is introduced in Harry Potter and the Order of the Phoenix. On the Hogwarts Express, Neville Longbottom proudly shows the plant to Harry Potter, Hermione Granger, Ron Weasley, and Ginny Weasley. To demonstrate its unique property, Neville prods it with a quill, causing it to spray Stinksap all over the compartment's ceiling and its occupants, including Luna Lovegood who entered at that exact moment. This event serves to highlight Neville's deep passion for Herbology and his growing confidence, even if the demonstration is clumsy. Later in the school year, the plant's name, “Mimbulus mimbletonia,” becomes the password to the Gryffindor common room. The password was initially met with disgust by The Fat Lady, but was later enthusiastically accepted by her temporary replacement, Sir Cadogan, who considered it a “swashbuckling” name.
The name Mimbulus mimbletonia is likely a combination of several roots.