Fern

Ferns are mentioned in the How to Train Your Dragon Book series when describing some island environments.

Description
Bracken

How to Train Your Dragon
The first book describes the Isle of Berk as having a lot of bracken.

"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