Groot is an alien known by the Kree as a Floral Colossus, though this species was once thought extinct. He was first seen when he landed on Earth and threatened humanity as one of the Marvel Monsters in the Marvel Age of Monsters. He was however soon defeated by a clever human witch caused Groot to flee Earth once more. He was not heard from for many years after his initial encounter with humanity.
Groot was created by Larry Lieber and Jack Kirby and first appeared in Tales To Astonish 13 (1960).
Major Story Arcs
Years later, Groot was recruited/apprehended by the Howling Commandos, despite his ability to hide in plain site by looking like a tree, because he smells nothing like a tree. Eventually, Groot was freed out of SHIELD custody and returned into Kree space. It is however unknown how he was freed and returned to space.
Some years later, Groot started changing his ways and became a force for the good. He joined a team of space superheroes, led by Peter Quill, AKA: Starlord. The group went to the planet known as Hala for an apparant suicide mission to stop a mass-assimilation weapon being developed by the Phalanx Covenant. During this mission, Groot is blown up and seemingly killed, though he is pleased to have this happen as he surveys the situation he's in and deems that it would be a good and honorable death. This is not to be, however, as part of Groot survives and catches up to the rest of his team. The twig-size Groot perches on Rocket Raccoon's shoulder for a time in a bit of turnabout as Groot's shoulder or outstretched hand had been Rocket's preferred gattling gun perch throughout the story up till then. Groot requests moisture and is spat upon by Rocket. Ignoble, but it helped.
Guardians of the Galaxy
Later, restored to full size, Groot again allows himself to be used for suicide tactics. He infiltrates a phalanx base and grows his limbs outwards into the base's command center before allowing himself to be blown up; taking the phalanx structure with him. Before he went off to die again, however, Rocket Raccoon had broken off a twig of him in the hopes that they would be able to grow him back again with it. After this mission, Rocket dutifully waters the Groot twig and in time he does return once more, now to join Starlord's new revamp of the Guardians of the Galaxy.
Much of Groot's dialogue is merely him saying "I am Groot!" again and again, which, strangely, allows him to function as comic relief. In Guardians of the Galaxy #17, Lord Maximus reveals that while it may sound as if Groot is only able to say "I am Groot!" he is actually saying quite a bit more. He can only say the same phrase because of the condition of his larynx, to truly understand him "you must listen to the sigh of breeze beneath it. The nuance of meaning." Groot is also extremely intelligent with extensive knowledge of quasi-dimensional engineering. With his knowledge, he and Maximus were able to stop Attilan from being consumed by the Fault. After saving Attilan, the team had to face the Fault itself. Adam Warlock was able to stop it's expansion by overlapping the time line with an unused future. But the future he used was the future in which he became the Magus. As the Magus, he immediately attacked the team. Groot tried to help, but the Magus was far too powerful and blew apart one of Groot's arms when he tried to attack.
In battle with the Magus, many team members were killed including Groot's friend Mantis. In the end, Starlord was able to revert the Magus back into Adam, but was forced to end his life. The Fault had been stopped from expanding and the Magus defeated, but the cost of the battle was very high. Following the disbanding of the Guardians after the war with the cancerverse. Groot was forced to return to Planet X where it was revealed he was not the true monarch of the planet but one of the younger members of his race. In pretending he was ruler, he was sent into exile to rot on an island far off the planet.
On Planet X Groot was exiled to a far off island where he was being guarded by "The Cyborg Punishment Birds" (Robotic woodpeckers.) Until his good friend Rocket Racoon stages a rescue. During this rescue attempt the robotic woodpeckers can no longer guarantee Groots containment so they unleash the most feared weapon on Planet X, FLAME. Groot is set a blaze right in front of Rocket Racoons eyes. It is revealed that Groot did not die because after all of the adventures with the GOG (Guardians of the Galaxy) he has become very good and creating smaller versions of himself or "cuttings". After this our dynamic duo are rescued by The Undergrowth Resistance of Planet X. A rebel group of small plants, small animals and fungi trying to win back rights from their Giant Tree Overlords. Groot had been one of their supporters before he joined the GOG.
Groot then accompanies Rocket to his home planet, Halfworld Asylum for the criminally insane. After Rocket Racoon gains his memories back the asylum is sent into chaos by Barry Bauman, The Star Thief. Groot pulls Rocket out of a holographic hallucination. Turns out earlier that Groot had taken the precaution of releasing a cutting of himself upon his initial capture incase of trouble, Groot also uses his Dendronic powers which allow him to communicate through any trees even holographic ones. Groot then leads a group of wooden clown security guards which he has germinated to control, on an assault of the ships support systems as a distraction for Rocket Racoon. After everything on Halfworld is settled Groot stays with Rocket Racoon to try and start back up the Guardians of the galaxy.
Shortly after leaving Halfworld, Rocket and Groot investigated a space pirating operation and after stopping it, found out that they were swept into the inter dimensional TV producer, Mojo's latest Reality TV idea. Using real life crimes that Rocket Raccoon and Groot would fight but instead of being the heroes. If an innocent was caught in the crossfire, they would be killed in the process. Now Rocket and Groot seek to stop Mojo but at the same time, if their show gets cancelled, they will die in the process. As Rocket and Groot moved from one setting to another, Mojo started advertising action figures with a collection pack that allows buyers to assemble their own 12" Groot figure after collecting all five. The demand was so high, Mojo stand to make a fortune until the Timely Inc. Mail Device decided to take his own action in stopping everyting and held a very large plasama rifle at Mojo's face. It allowed the reality system to stop just enough for Rocket Raccoon and Groot to leave their fictional landscape and head straight towards Mojo's base.
Groot is a sentient giant Tree from the Planet X. He has super strength due to his enormous size and was mostly used as a heavy assault trooper by the Guardians of the Galaxy.
Groot has shown the ability to create multiple miniature copies of himself known as cuttings which retain all his memories and can be used to resurrect himself if he is destroyed. Cuttings can also germinate other plant life forms so Groot can control them.
Groot can also speak through trees of all forms and has even spoken to Rocket Racoon through holographic trees that were not even real but just made up in Rockets head.
Even though Groot only ever says " I am Groot" It was revealed by the Inhuman Maximus that Groot actually has a very vast intellect. It is never commented that this may also just be due to Maximus's battle with sanity.
In Other Media
The Avengers: Earth's Mightiest Heroes
Groot (and the rest of the Guardians) appeared in the episode "Michael Korvac." Groot was voiced by Troy Baker.
Groot is set to appear in the 2014 film Guardians of the Galaxy directed by James Gunn.