Bamboo

Bamboo is a plant seen in the movie short, Legend of the Boneknapper Dragon.

Description
Bamboo is a very tall, hollow grass in the Subfamily Bambusoideae. It is very prolific and can out compete other plants and grow tightly packed together. Some species have been known to grow 3 feet in 24 hours. Bamboo is most known and cultivated in Eastern Asia, but some species can be found around the equator in Africa and South America. It is doubtful that historical Vikings ever came across bamboo.

Function
In the How to Train Your Dragon Franchise, bamboo appears only as an obstacle for Vikings (specifically Gobber) to get through.

In reality, bamboo is a widely used plant with many uses. It can be used as a building material, for food, tools, furniture, historically as a writing surface, weapons, textiles, and musical instruments.

Legend of the Boneknapper Dragon
Bamboo appears on an Unnamed Island that Gobber was on in his younger years. As he was trying to escape the Boneknapper, he uses an egg beater hand attachment and chops through a forest of bamboo.