Dragon Root

Dragon Root is a plant known to grow underground on the Isle of Berk. It is the exact counterpart of Dragon Nip: instead of making dragons calm, it makes them very aggressive. Even trained dragons will try to attack each other, but the dragons' riders can calm them down to a state of wariness, until the dragon root can be removed from their presence.

It seems that most dragons would be affected by dragon root. However, for unknown reasons those with a rock-based diet, such as Gronkles, are immune to it.

Appearance
Dragon Root looks like a stumpy and somewhat misshapen cactus, with hair-like parts sticking out of different ends. They are green in colour with white roots.

Lore
In "A Tale of Two Dragons", the riders were clearing Mildew's cabbage field when Hookfang and Stormfly started to fight. It was later sensed by Meatlug while she and Fishlegs were investigating the spot where the fight started and she uncovered it in the field. When Hookfang and Stormfly started fighting again, Barf and Belch got too close to the root and started to act crazy as well. While Toothless held Barf and Belch and Hookfang knocked them aside in order to calm them down, Astrid and Snotlout calmed down their dragons enough and used Hookfang's wing clap and Stormfly's single spine shot to help Meatlug remove the root and fly out to drop it into the sea.

It also made an appearance in "Cast Out Part I", where Dagur used it as a trap for Hiccup in order for him to surrender Toothless to him. He left it inside the Academy so that the dragons would begin to fight over it, and Hiccup would come to stop them. In "Cast Out Part II" Fishlegs used it to lure the Screaming Death to Outcast Island, after doing that he dropped it into the sea just like the last one so the Screaming Death would stop following him.

Dragon Hunters stew up the root and coat the head of their arrows in it, so they can stung dragons and make it easier to capture them.