A Plangentine is presumably either a fruit or a flower. Bathilda Bagshot stated that she first saw Ariana Dumbledore while out gathering Plangentines on a winter's night in Godric's Hollow. It is unknown if it is used in potions or not.
The term Plangentine is composed by the word plangent meaning resounding, noisy, deafening, thundering, piercing, booming, shrill and vibrant. Besides, this is derived from Latin plangere which means cry, yell, scream plus suffix -ine.
- Harry Potter and the Deathly Hallows (Mentioned only)