Yasei no Bara

Wild Rose

From Storm in Heaven:

Saotome Masahiko is a plant fanatic who just transferred into his dream school, where he finds out that one of his classmates, Tendou Tasuku, is actually a highly-evolved plant. Tasuku is aloof and not exactly fond of humans, but can Masahiko's innocence win him over? Despite their differences, is it possible for super plants and humans to coexist side by side …and even become… friends?