"Heather" can describe a number of plants in the Family Ericaceae, in the Genus Cassiope, Genus Erica, and Genus Calluna. The latter is most likely the type of heather referred to in the Book series, as it is common in moorland environments and is widespread on the British Isles and Scandinavia. The only species in this Genus is Calluna vulgaris. It is a small shrubby plant with lilac-colored flowers and small, connected leaves surrounding it.
In the Book series, heather is a common background plant found all over the Isle of Berk.
In reality, it has been cultivated as an ornamental plant. It has also been used historically as a dye plant, producing a yellow color, as well as for use in leather tanning. It is edible and has been used to make various ales and beers. Heather can be grazed upon by sheep, especially in cold weather.
Medically, heather may cause allergies in some individuals, such as Fishlegs.
The first book describes the Isle of Berk as having a lot of heather.
|“||You didn't really walk on the island of Berk, you waded - through heather or bracken or mud or snow, which clung to your legs and made them difficult to lift.||”|
|— How to Train Your Dragon|
|“||Running through heather is not unlike running through knee-deep molasses, and they kept disappearing up to their knees in the bog.||”|
|— Book 1|
In the environment of Berk, the heather remains wet, which helps retard formation of a wildfire from Dragon flame.
|“||The heather was damp, however, and the blaze flared for only a few moments, then extinguished itself.||”|
|— Book 1|
The Isle of the Skullions is mentioned as having "high ferns and endless heather". The heather on this island is mentioned again later when Fireworm vomits from the stench emanating from a treasure chest and as a hindrance to Hiccup as he flees from predatory Skullions.
Heather is mentioned when Hiccup looks out of his prison window at the unrelenting rain beating down the heather, located at Fort Sinister.
Heather is mentioned as one of several things Fishlegs is allergic to.