Vin Diesel to Join Guardians of the Galaxy Rumour has it that Vin Diesel is set to join the cast of Guardians of the Galaxy, the upcoming Marvel superhero film based on based on the Marvel Comics superhero team of the same name. According to Deadline Diesel will be joining the cast as tree-like alien Groot. Groot gathers strength by absorbing wood and can control trees. We think Vin Diesel will be excellent as Groot, he’s always been a bit wooden (Sorry, we couldn’t resist). Guardians of the Galaxy is slated for an August 2014 release.