4. Arundo donax (giant cane)

Arundo donax, or giant cane, is a weed that could be cultivated for biofuel.

Able to grow almost three inches per day in the summer, giant cane (Arundo donax) could be the superhero of the biofuel world, producing multiple harvests every year on poor soil. Left unmanaged, though, it turns to the dark side. At least six states from California to Maryland have reported it as an invasive species.

Image: Shizahao on wikimedia.org (creative commons license).