Spinach

Spinach refers to a plant briefly mentioned in How to Train Your Dragon Book series.

Function
In the Book series, spinach is mentioned as a way to illustrate intense green color.

How to Cheat a Dragon's Curse
The intense green color of Doomfang eyes is described in depth, relating them to the color of green spinach.

"It was as if all the green in the world, of peas, of grass, of spinach, of leaves, of beans and frogs, had been concentrated in that one eye and given it the intensity of pure green acid."

- Book 4