Are you talking about a poison dragon in dragon vale? If so then you have to breed a plant dragon with a fire dragon. Keep in mind that the dragon on the left side has to be a plant dragon, otherwise you'll end up with a flower dragon.
The poison dragon unlocks at level 7.
A lichen, poison, bluefire, or frostfire dragon.
You get a poisonous tree dragon.
It will make a lichen dragon
a flower dragon or a poison dragon
Dragon Scimitar for sure. But get both and your awesome because poison and strength scimitar!
Flower dragon
You have to breed a plant and a fire dragon.
You could either get a Flower Dragon or a Poison dragon.
Three of the possibilities are tree dragon, poison dragon, or lava dragon.
Either a poison dragon or a flower dragon
You have to breed a plant and a fire dragon.