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If Groot hadn't been turned into fertilizer at the end of Infinity War, how much taller would he be in Endgame? Regardless of how much of a time jump there is between the two Avengers films, would Teen Groot have another growth spurt in the real-life year gap between the movies?
Yes, one avenging arborist tells SYFY WIRE. In fact, based on how tall Groot has been in his three Marvel Cinematic Universe appearances, we can pretty accurately determine his growth rate, though there are still some questions.
"There are a few confusing things about Groot," admits Eric North, an assistant professor of practice at University of Nebraska-Lincoln's School of Natural Resources who specializes in urban and community forestry. "It's difficult to imagine what Groot is actually growing off of, assuming he has a carbon-based, wood-like structure."
Real trees use energy from photosynthesis to absorb carbon from the atmosphere, and that carbon becomes their physical "body." Given that we don't see Groot eat anything but one of his own leaves in the first Guardians of the Galaxy, and some candy in Vol. 2, North presumes Groot must have stoma, the structures on the underside of leaves that absorb carbon, and he might use radiation from space rather than sunlight for energy.
Whatever Groot's eating or absorbing, it's apparently enough for a growing boy, but there are other factors when it comes to determining growth rates.
"We can sort of think about tree growth rates by looking at where trees are ecologically. After a forest fire, there are trees that come in called pioneer species. They grow very, very fast, and don't tend to live very long," North says. "The longer something lives, generally speaking, the slower it tends to grow."
Although Groot had quite an impressive growth spurt between his appearances in Guardians of the Galaxy Vol. 2 and Infinity War, he's starting to slow down, which speaks well of his possible longevity — Thanos' snap notwithstanding.
"You might think of Groot almost like a redwood, where he grows pretty quick in the beginning and then stays this big giant size for a long period of time," North says, adding that Groot could also be compared to a more tropical tree like a ficus or fig.
When Rocket plants one of Groot's twigs at the end of the first Guardians, the little guy looks to be about 6 inches tall. In Vol. 2, which is set two months later, Baby Groot is 10 inches tall. Infinity War takes place roughly four years after Vol. 2, and Groot stands a slender 5 feet, 4 inches tall. (This Groot is often called "Teen Groot," but James Gunn has said that Groot is an adolescent, more akin to a 12-year-old than a teenager).
"I calculated a growth rate chart that sort of looks like Groot, given the few data points that we have for Groot's height and age, so I calculated a polynomial function that would fit with the data we have," North says, explaining that arborists typically use power functions or exponential functions to explain tree growth rates, since they're non-linear. "At the very beginning of a tree's life, it grows very quickly until it gets to some age, which varies by tree, and then the growth rate tends to taper off and slow down."
North created two possible charts — one that assumes Groot's initial Guardians of the Galaxy height of 12 feet, 4 inches is fully grown (an exponential function), and one that assumes he'll keep growing forever (a power function). Of the two, the latter scenario might be more accurate, as Vin Diesel likened the first Guardians Groot to a "college freshman" rather than a fully grown adult.
According to this model, Groot would have grown to be just under 6 feet tall in the year since Infinity War. It would take roughly two decades for Groot to grow back to his original height as seen in the first Guardians.
If Groot survives, and Disney keeps making Guardians of the Galaxy movies for another century, North says Groot would be 28-and-a-half feet tall in 100 years.
North can't exactly compare Groot's rate of growth to any real-world tree, because species-specific rates are difficult to calculate. However, the arc of his growth does look similar to the way real trees grow.
Although Groot has been steadily growing throughout his film appearances, he does display the ability to instantly grow long roots or viney tendrils that he uses as weapons. How he can do this so quickly but take years to get taller is a mystery, and it's far faster than even the speediest ficus or strangler fig.
But, North says some real plants do have some super-fast abilities.
"There is something called jasmonic acid that happens in plants. It's a hormonal response to herbivory," North says, explaining that some plants can flush themselves with this acid as soon as they "realize" some bug is eating them. This makes the plant unpalatable, and it takes place in a matter of seconds. Not as cool as a giant wooden lance, granted but a pretty neat trick.
"So, while plants don't have that [instant growth], they have the ability to very quickly send chemical signaling," North says.
One thing is clear, though. However tall Groot ends up getting, and however long it takes, his vocabulary certainly isn't growing at a similar rate.