Where did Groot come from? In reality, he came from the imaginations of Jack Kirby, Dick Ayers, and Stan Lee. In the Guardians of the Galaxy movie, he came from another planet. In this essay, he came from the stuff in your yard. We'll see which plants might have evolved, over time, to become the world's most beloved tree-man. Warning: Major spoilers for the movie after this point!
The African Daisy
At one point during the Guardians of the Galaxy film, Groot pauses to make the world a little more magical for a kid by giving her a flower. At first, the delicate color of the flower makes it seem like an apple blossom, but on closer inspection it appears to be a kind of daisy. The daisy is part of the family Asteraceae, which includes daisies, asters, and sunflowers. We all think of daisies as having bright white petals surrounding an even brighter yellow center, but Groot's flower looks more like an African Daisy (pictured on the bottom right of the poster below). This species that comes from South Africa and has white petals that deepen to purple around the center of the flower. Or it has yellow petals that deepen to brown at the center. Or it has oddly tapered and flared petals, shaped like dew-drops, that are purple and yellow.
The fact is daisies have a lot of variation. They should, because humans have been playing around with Asteraceae for thousands of years. They're the domesticated dogs of the plant world. They come in all different colors, sizes, and shapes. They survive in wildly varied habitats. They can be shrubs and long-stemmed flowers. They were grown in temple gardens in Egypt and cultivated in Europe as medicinal plants that could reportedly cure eye problems and ulcers. If you want to breed a sentient plant that has a very specific set of qualities and is friendly with people, these are probably the plants to start with. I'm not the first to think so; Luther Burbank, a famous horticulturalist at the turn of the last century, used African Daisies in his book Shortcuts Into the Centuries as an example of how humans should stop waiting for evolution to just happen, and breed plants to their specifications. Granted, he merely described how humans sped up evolution by purposely cross-breeding the white African Daisies with an orange daisy and creating a pink daisy, but it's a start.
We don't even need to set out to make a walking tree to get a walking tree. The family Asteraceae are fairly good at crossing over with wild plants. One study done on sunflowers showed that a few extra volunteer plants sprang up in a field of cultivated sunflowers — "volunteers" being what botanists call plants that spring up from seeds or cuttings made by cultivated plants, but which haven't been cultivated themselves. These volunteers act as gene intermediaries between cultivated and wild plants. Genes inserted in cultivated plants are inherited by volunteers, and volunteer flowering (and pollination) time overlaps with wild plant populations, allowing the genes extra opportunity to flow from cultivated plants to wild ones. The researchers speculated that it's even possible that the volunteers can spread and establish "feral" populations with modified genes. Who knows what can happen from there?
The Sycamore Maple
Here you can see Groot displaying a new power. The glow is eye-catching, but for now let's focus on the fact that Groot can produce samaras. Samaras are winged seed cases; they can be anything from the minuscule fluff on a dandelion to winged gliders the width of a human hand. At first, I though the samaras that Groot produces made him the descendant of the Burmese lacquer tree. What a fool I was. Burmese lacquer trees are beautiful, but not hardy. They're endangered. They would also make terrible team-mates, as their sap and sawdust cause irritation and inflammation of the skin. A Burmese lacquer Groot could never carry out a selfless rescue mission without giving all his teammates rashes with his splinters.
Although the lacquer tree pods do look similar to Groot's samaras, Groot is more likely to be the product of the evolution of the sycamore maple. This species usually produces samaras in groups of two, which look like bat wings, but it's not unusual for certain trees to diversify and create samaras of three or four, giving them a true helicopter appearance. The tree is urban-friendly and can take pollution, cold, high-concentrations of salt, and responds well to having parts of itself hacked off. It's sometimes sold as a bonsai tree, and trained into certain positions.
If Groot isn't a direct descendant of the Acer pseudoplatanus, the sycamore maple, there's a good chance he's a close relative, and also of the genus Acer. Acers thrive as transplants. The sycamore maple is well-known in the United States, but originates in Europe. It's been followed across the pond by its relative Acer platanoides, or the Norway maple. Acer platanoides has established itself quickly, and it hasn't been content to stay on the sidelines, springing up in industrialized areas or newly-cleared ecosystems. It's elbowing aside well-established, old growth forests, prompting scientists to come up with the deliciously-named Enemy Release Hypothesis.
There are some life forms that are adapted to their own environment and, should they be transplanted somewhere new, will be devoured by the tougher predators and parasites in their new ecosystem. In contrast, there are some lifeforms that are barely kept in check by their "enemies" in their own environments. Transferring them somewhere new will let these superbeings proliferate wildly.
Let's say a well-designed samara from an enterprising Acer got caught up in the wake of a spaceship visiting Earth. As we see in the movie, space ships visiting Earth are not that unusual an occurrence. A bit of solar wind, a bit of luck, and the seed lands on a planet where it can basically take over. Many generations later, there is Groot the indestructible. (Finally, the picture to the left is a cutting of the sycamore maple that is growing a new bud. Does it look like something you've recently seen on screen? Perhaps while the Jackson 5 were playing? I'm just asking.)
The Honey Mushroom
This brings us to Groot's most mysterious quality — he produces light. This surprises everyone in the film, including any botanists watching. Bioluminescent plants are very recent additions to the world, and are made by humans. If Groot were a descendant of any of these plants, he'd have to be very young indeed. On the other hand, bioluminescent fungi have been around, world-wide, for quite some time.