|“||Hiccup, Did you know that the Sneeze Wart bush can grow up to three-feet tall with a hairy stem and serrated leaves?||”|
|— Fishlegs in "Darkest Night"|
No plant with the above description and name exist in reality. However, there is a 'sneezewort' (Achillea ptarmica) plant. It is not a bush, but rather a flowering perennial with small white five-petaled flower clusters. The sneezewort is native to Europe, but occurs in North America also.
The Sneeze Wart bush has no known function in the DreamWorks Dragons Franchise.
Sneezewort leaves, however, are edible to humans, but poisonous to some other herbivore animals such as sheep. The leaves can be ground to make a 'sneezing powder'. Sneezewort has also been used for various ailments in herbal medicine.
In the episode "Darkest Night", Hiccup faces some tough decisions, and feels that his father would not have become injured if he never shot down Toothless in the first place. Astrid tells a story to make him feel better, about how Berk and the Dragon Riders would have ended up if he didn't shot down Toothless. In it, Fishlegs have information Plant Cards, rather than his Dragon Cards. One card he shows Hiccup in the story is the one for Sneeze Wart.