|— Book 4|
The potato (Solanum tuberosum) is a low-slung plant which produces small flowers somewhat resembling stars. Depending on variety, the flowers may be white, purple, pink, or red. Fruits are small, green, and circular. Potato plants also store nutrients in a tuber - a type of specialized stem. They can also propagate asexually from the tuber. It is the tuber which is of importance to humans. All other plant parts - stems, flowers, leaves, and fruit - contain high enough levels of Solanine to be toxic.
Potatoes have been cultivated in and around the Andes in South America for thousands of years. The Spanish introduced the potato to the rest of the world in the 1600's. Vikings would not have encountered the potato, even those who journeyed to far Northern America.
Although considered a mythical object amongst the majority of Vikings in the Book series, it is the only known cure for Vorpentitis. Once digested, the person (or creature) is forever immune to Vorpentitis.
In reality, the potato tuber is used for consumption, not medicine.
Hiccup, in the epilogue, also mentioned potatoes were good mashed or with butter just like how we eat potatoes.
Despite the mythical status the potato has in Book 4, the potato is mentioned by name by Alvin the Treacherous, who is trying to convince the Hairy Hooligan Tribe that he is merely a potato farmer and accidently came across the coffin of Grimbeard the Ghastly.
|“||I am a poor-but-honest farmer, and a long time ago in the Peaceable Country, far far away, I was digging up some ground for ... er ... planting potatoes when I came across this coffin which ... er ... just fell open in my hands.||”|
|— Alvin the Treacherous|
Ziggerastica utilizes the word potato when uttering one of his colorful descriptions of Hiccup and humans in general.
|“||By the way, O-Boy-With-a-Nose-Like-a-Small-Potato, your friends are even uglier than you are! Where did you find these people? Never in my life have I seen anybody who looks so much like a lemon sole ...||”|
The potato was only found when Norbert the Nutjob's father, Bigjob, brought it back from America. However, along the way, he was killed by the Doomfang. The Hysterics had kept it on their island until Hiccup stole it to cure Fishlegs of Vorpentitis. The potato was eaten by the Doomfang on the return journey because it too had Vorpentitis. It was later found out that Hiccup himself had Vorpentitis and that Fishlegs just had a very bad cold. Later on, a few seeds that clung to an arrow grew into potatoes on Berk so that nobody else ever died of Vorpentitis.
In Book 4, Hiccup does not know what a potato looks like and tries to imagine it.
|“||Because, of course, he did not have any idea what a potato looked like, whether it was orange, or green, or large, or small. Hiccup had somehow imagined it as RED with little black spots, and kind of oblong, or triangular, just because it sounded so exotic. Purple perhaps? Really, he hadn't a clue.||”|
|— Book 4|
When Hiccup finally sees the potato in a box held by a frozen Bigjob, he thinks it a "round, rather disappointing shape of a lump brownish vegetable."
|“||Whomsoever removes the Arrow from this Vegetable Shall Rid Us of the Doomfang and Prove Himself Right True Hero and Ruler of all the Viking Tribes.||”|
|— Inscription from Book 4|