The Blue Oleanders are a species of oleanders seen in How to Train Your Dragon franchise. They are poisonous to reptiles, including dragons. The only way to cure them is if a cure is made from the venom of a Scauldron.
Appearances[]
Dragons: Riders of Berk[]
In "Dragon Flower," At some point, Trader Johann acquired Blue Oleanders and sold them to Mildew on Berk. He later planted them on the island in another attempt to get rid of the Dragons, they end up getting sick.
The oleanders are first noticed by Astrid when she, Hiccup, Toothless and Stormfly are out flying when suddenly, Toothless gets dizzy. At first, the Riders realize that anything they bought from Trader Johann might be the cause of the dragons' sickness so Hiccup commissions for everyone to get rid of anything they got from Trader Johann. However, Hiccup and the others were sad to see that none of the dragons are recovering. Just after Stoick returns with Thornado getting sick like Toothless and Stormfly, the Dragon Riders and Stoick find blue flowers that they never noticed before. Tuffnut admits that he saw Mildew planting the flowers the other night, causing Stoick, Hiccup and Astrid to confront the old man about it. He feigns ignorance that the flowers made someone sick.
Later, Fishlegs used his botany book and identified the flowers as blue oleanders, which are poisonous to all dragons, except the Scauldron. With this information, Hiccup, Stoick and Gobber went on a quest to find the Scauldron, taking a reluctant Mildew with them, who Stoick blamed for putting them in this position in the first place. They lure a Scauldron with blue oleanders, which attacks the ship and engaged in a battle with the Vikings. During the attack, the Scauldron sees a blue Oleander on Mildew's butt and bites the flower while injecting Mildew with its venom. At first, Hiccup, his dad and Gobber are upset because they were unable to retrieve the venom, until they hear Mildew complain about it being in his bloodstream.
When the Vikings return to Berk, Gobber extracts the venom from Mildew and used it to create an antidote for the dragons, thus curing them from their affiliction. Traumatized by this, Gobber gives Hiccup the cure for blue oleander poisoning before going off to scream into the woods.
The Dragon Riders distribute the cure to Toothless and the other dragons, who all make a speedy recovery and foiling Mildew's latest attempt at getting rid of the dragons.