Warning: SPOILERS for Guardians of the Galaxy Vol. 2 ahead
Marvel Studios' Guardians of the Galaxy introduced Groot, then Guardians of the Galaxy Vol. 2 featured a Baby Groot version of the sentient tree-like creature - so what will the character look like in Guardians of the Galaxy 3? The Marvel Cinematic Universe kicked off with Iron Man in 2008 and concluded Phase 1 with The Avengers in 2012; all throughout, the adventures of Earth's Mightiest Heroes and the shared superhero world were relegated to Earth. That is, until James Gunn's 2014 space opera/comedy, Guardians of the Galaxy, which introduced movie fans to a team of not-quite-heroes.
The team in Guardians of the Galaxy included Peter Quill aka Star-Lord (Chris Pratt), the assassin Gamora (Zoe Saldana), Drax the Destroyer (Dave Bautista), and the duo of Rocket Raccoon (Bradley Cooper) and Groot (Vin Diesel). The team is back for Guardians of the Galaxy Vol. 2, though their roster expands to include former villain/Gamora's sister Nebula (Karen Gillan), the former leader of the Ravagers Yondu (Michael Rooker), and the empath Mantis (Pom Klementieff). However, there was one notable change in the main team from the first movie to Guardians of the Galaxy Vol. 2.
We are, of course, talking about Groot. In the 2014 film, Rocket Raccoon's companion seemed to be of an adult age - though it wasn't quite clear how old either he or Rocket were at the time. But in the Guardians' final stand against Ronan (Lee Pace), Groot sacrificed himself to save his friends and it seemed he had died in the process. A credits scene for Guardians of the Galaxy however, revealed he had reverted back to a sapling, planted in a pot on the Milano and dancing behind Drax's back - reaffirming the character as a fan-favorite for many. When Groot returned for Guardians of the Galaxy Vol. 2, the character did so as a toddler-aged version. Now, with Groot continually growing, it begs the question of what he'll look like in the already confirmed Guardians of the Galaxy Vol. 3.
For those fans hoping Baby Groot will return in another MCU movie, one of the Guardians of the Galaxy Vol. 2 credits scenes confirms that won't be the case for the character's next appearance. During one of the sequel's five end credits scenes, Groot is shown as a teenaged version of himself in his room on the Milano and it's a typical teenager's room, mess and all. Although it's unclear how much time has passed since the end of the movie and this particular scene, it must be quite a few months - if not a year or more. In fact, only a few months had passed between Guardians of the Galaxy and its sequel, so we know Groot grows at an accelerated rate compared to humans. If he could grow from an infant in a pot to a toddler in just a few months, then he could certainly age from a toddler to a teenager in a few more months.
Of course, while this end credits scene unfortunately means viewers won't see Baby Groot again within the MCU - at least, anytime soon - it likely also acts a bridge between Vol. 2 and Groot's next appearance. It confirms an older version of Groot than the teenager will appear next, similar to how the potted Groot teased Baby Groot but was still younger than the version of the character that appeared in Vol. 2. However, Guardians of the Galaxy Vol. 3 isn't Groot's next appearance in the MCU.
Groot will appear alongside the rest of the Guardians of the Galaxy in the next two Avengers installments. Although the entire lineup of Guardians team members who will appear has yet to be officially released, a number of cast members have been confirmed through set photos or interviews - such as Gillan as Nebula, Pratt as Star-Lord, Saldana as Gamora, and Bautista as Drax. Of course, in the case of Rocket and Groot, it's a little more difficult to determine whether they're in the film since they're CGI-created characters and their actors don't need to appear on set. However, with the other Guardians all showing up to fight against Thanos, we can presume Groot and Rocket will be there as well.
As for how old Groot will be in Avengers: Infinity War, that remains to be seen. It's unclear exactly how much time passes between Guardians of the Galaxy 2 and Infinity War, but Marvel Studios chief Kevin Feige recently commented on the fact that Marvel movies don't overlap anymore in terms of the timeline like they did in Phase 1. Instead, they tend to happen in real time. While Marvel has more leeway in terms of the Guardians series continuity since it's almost entirely removed from Earth, it's possible Vol. 2 will line up with the rest of the MCU - meaning, Guardians of the Galaxy 2 takes place at least a year before Infinity War. If that's the case, we'll likely see an adult aged Groot in Avengers 3 and 4, similar to the character's age in the first Guardians of the Galaxy.
In terms of the third Guardians-focused film in the MCU, we know based on Gunn's recent comments that Guardians of the Galaxy 3 falls in the timeline after Avengers: Infinity War and Untitled Avengers 4. So, we know Groot will be older in Guardians of the Galaxy 3 than he is in both Infinity War and Avengers 4 - that is, assuming he doesn't sacrifice himself again and revert back to a sapling. Without a release date for Guardians of the Galaxy Vol. 3 - though we do know it will arrive at some point in Phase 4 - or any indication of where it will fall not only in the MCU timeline but the team's own series, it's difficult to determine how old Groot will be or at what phase of his life he'll be.
That said, the character's voice actor recently made some comments that could provide a hint. In a recent interview, Vin Diesel said we haven't seen full-grown Groot yet within the MCU - not even in Guardians of the Galaxy. According to the actor, that iteration of Groot "was a freshman in college" while Baby Groot is in nursery school. So, depending on how much time has passed between Avengers 4 and Guardians of the Galaxy 3, the threequel will potentially feature a full-grown Groot - or, it's also possible Marvel is holding onto the fully grown version of character for a Groot spinoff film with Rocket Raccoon.
If Guardians of the Galaxy 3 is the last we'll see of this iteration of the team, then Marvel could certainly be setting up the fan-favorite duo for their own theatrical outing. And, if that's the case, it would make sense to leave a little more room for growing up/character development when it comes to Groot. That is, of course, only speculation for now since Marvel won't announce its Phase 4 films for some time.
Still, in terms of Groot growing up through his next handful of MCU appearances, it's likely we'll see a similar version of the character from Guardians of the Galaxy in Avengers: Infinity War and Avengers 4, with Guardians of the Galaxy 3 potentially including a full-grown Groot. Of course, there are a number of factors that will affect Groot's aging throughout the MCU - including how much time passes between his appearances and whether any outside forces will be a setback to his progress - but one thing is for sure: Guardians of the Galaxy Vol. 2 is the last we'll see of Baby Groot.