A Forest Flame is one of the type of flames of the Dying Will Flames of the Earth.
Overview
Forest Flames are shaped like countless leaves forming sharp edges. Forest Flames allow the manipulation of plants. Its user can grow, manipulate, and use all sorts of forest-born vegetation to a certain level.
Kouyou Aoba used it to recover all the plants on Simon Island. Koyo also used it to create a barbed vine cage as an arena.
The Flame also has the sharpness of a blade, comparable to small, but very sharp knives. This was shown when Ryohei Sasagawa was knocked back by the leaves, severely wounded by cuts inflicted by the Flame.
Gallery
Koyo activating his Simon Ring.