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The tree small giant creatures resembling people usually with beards are present in many fantasy stories, but that's it... it is fantasy. From a scientific viewpoint how would such creature even exist in the first place? How does it function?What does it do to stay alive?Can they evolve or is advanced technology needed to create them?

This question is part of the Anatomically Correct Series.

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    $\begingroup$ Exactly the same problems as with normal giants, unless you have some ideas to overcome them and you didn't share. $\endgroup$
    – Mołot
    Commented Aug 22, 2016 at 21:12
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    $\begingroup$ usually ents are roughly the size of a very tall person or a small tree...This one in the pick is from a game, roughly a few centimeters taller than my character...which is 280-300 centimeters in height $\endgroup$
    – Charon
    Commented Aug 22, 2016 at 21:20
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    $\begingroup$ Question describes them as giants, and by Tolkien (who as far as I know invented the name) oldest Ent was " at least fourteen foot high". Depends on foot used, that's 4 to 4.5 meters - as defined by Ents' author. If you want to forget their size, please state it directly in question. "Small giant" is kinda confusing". $\endgroup$
    – Mołot
    Commented Aug 22, 2016 at 21:29
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    $\begingroup$ Don’t be so quick to accept an answer! Wait at least 24 hours, for people in different time zones to weigh in. $\endgroup$
    – JDługosz
    Commented Aug 22, 2016 at 23:51
  • $\begingroup$ See the aliens invented by Robert L Forward in Marooned on Eden. $\endgroup$
    – JDługosz
    Commented Aug 22, 2016 at 23:55

6 Answers 6


See the aliens invented by Robert L Forward in Marooned on Eden.

This author is renowned for his “hard” SF and real science contributions to lightsails, tethers, gravitonomy, etc.

So when he turned his attention to an intelligent and semi-mobile tree, he came up with unique solutions.

The roots move, slowly, by hydrolic power. This provides for overall motion of the being.

But there are detachable parts—possibly symbotes that became part of the lifeform much earlier in the evolutionary process. In particular the “eyes” can fly off and come back to dump data; and the “hands” are also small animals that are controlled somehow wirelessly at close range but have some small autonomy for doing more remote work.

The lifestyle, including complete sessile juvenile stage and sexual behavior, is described in the novel and a sequel.

So, I would suggest hydrolics for movement rather than muscles, and strong symbiosis for complete being: like how eucaryotes took in other bacteria to form organelles, the symbiosis would combine animal and plant characteristics at a very deep level.

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    $\begingroup$ that sounds more like a huorn than an ent $\endgroup$
    – James K
    Commented Aug 23, 2016 at 0:38
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    $\begingroup$ What’s the difference? The OP was fairly general about “tree people” as seen in a variety of fantasy stories, with a desire to bring it to science fiction. Forward did exactly that, writing hard SF, not fantasy. $\endgroup$
    – JDługosz
    Commented Aug 23, 2016 at 1:22
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    $\begingroup$ But are they made out of neutronium? $\endgroup$
    – John O
    Commented Apr 6, 2023 at 17:16

I think that Ents (as presented in Tolkien) are not actually plants but are actually a species of animal which resembles trees as a technique of camouflage.

This makes sense because, historically, the word Ent just means 'giant' and has been used pre-Tolkeien to describe giants, orcs and trolls, not just living plants. Tolkien Law says that Ents were created by the Gods to protect the trees from the Dwarves so there is no reason that, when created, they should themselves be made of tree.

Towards the beginning of time, Trolls were also made as a cheap imitation of Ents which suggests that Ents used to look more . Historically, the word 'ent' troll-ish and less tree-like.

Finally, the fact that Ents in Middle Earth are dying out because of the lack of entwives suggests that Ent reproduction is more similar to human biology than tree biology. So in answer to your question, Ents don't have to live that differently from us because they are just big people that look like trees.

Although I admit i might be wrong, its been a while since I read the books

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    $\begingroup$ It is not uncommon for plants to reproduce sexually. Many trees come in male and female varieties, the presence of a male and female member of the species isn't inconsistent with tree biology in the slightest. $\endgroup$ Commented Apr 6, 2023 at 17:21

How does it function?

As in lord of the rings Ents are slow moving often standing still for years. I always suspected they where trees that grew roots very fast and could leave them behind maybe even leech from other trees, like in a symbiotic relation. They are not called "tree herder" for nothing.

What does it do to stay alive?

Like trees they need water, CO2 and nutrients, As I said above they have a symbiotic relation to trees. They protect the forest in exchange for leeching nutrients from regular trees.

Can they evolve or is advanced technology needed to create them?

Maybe they will take over the world after we die out. Who is to say they don't exist yet but move so slow we can't even see it.


How would an Ent evolve. Very slowly, I assume - maybe something can be done with some interesting plants, a handful of coincidences, and a lot of time.

In any case, since of the traits we want, mobile is probably the rarest (among those that actually exist), I thought of tumbleweeds, and of carnivorous plants, and even the sensitive plant. That might be a good place to start. Of those, I picked the carnivorous plants, like the Venus flytrap or Waterwheel plant, or maybe even a Bladderwort. These are active traps, where the plant is triggered and moves to catch the prey, so it has some sensory feedback and movement already in its repertoire (unlike passive traps like flypaper, pitfall, or lobster-pot traps). Carnivorous plants are also known to grow in poor soils, one of the reasons that they turn to carnivory in the first place.

So, we have a carnivorous plant, and it is already sensitive, and a little bit mobile. Since catching its prey is a major investment of energy - it needs to grow shut, and too many missed snaps, or even too many feedings, can overreach its resources and it dies - it is already on the path to increase its sensory capabilities as much as it can. Since it already habituated to poor soils and difficult growing habitats, it is a good candidate for a flying plant - that is, growing with its roots not in the ground (on an outcropping of rock, or on dead wood, or on the living branches of another plant - not flying, flying, ok?).

Somehow, in some way, the plant (I picked the Venus flytrap, to be specific) ends up in more fertile ground - dropped by some bird, or carried by an animal. Just to up our chances, we should design a geographic proximity so that this happens often enough for a while, perhaps a raised bog with rock outcroppings separating it a more fertile growing ground below, with maybe some bird looking there for twigs for its nest, or something - since our plant will like both the bog and the outcroppings, and it might find the valley right for evolving in. When the seeds or cuttings land, the places most like its natural habitat, and therefore where it is likely to germinate, are the places already mentioned as "flying", the outcroppings of rocks and branches.

Of those, those which end up in the branches of a living tree have the opportunity to change in a new way, to adapt to their new growing condition. With sudden proximity to nutrients in plant-accessible form, in the tree next to them, some may find a way to grow partially parasitic (hemiparasitic, to be specific). Parasitic plants have evolved before, so it isn't impossible - especially since our plant will need to get water and mineral nutrients from somewhere, if the amount that germinated it was a thin layer on a living branch. If it can figure out any mechanism to tap into the branch, it may find itself a successful symbiote - since it may trap insects harmful to its host, and will not have to face much competition from its own kind in tree branches. This was one reason to pick the Venus flytrap as our base, since it specializes in slightly larger prey like beetles, which might let it avoid necessary pollinators (unlike species targeting smaller aerial insects as prey).

So, we have a carnivorous, semi-parasitic plant. With the slow adaptation of its roots to feed from the host plant, our plant now has resources - resources it lacked in its environment of poor growing soil - to evolve some more. Perhaps it can increase its sensory capabilities, and centralize its ability to act on those senses - the better to select the right kind of prey, and to prevent wasting energy on falsely triggered snaps. Perhaps it should tweak its reproductive strategies to better colonize its new growing grounds, to keep the species in the trees. Since it is already partially mobile, maybe it can take advantage of that, instead of trying to make fruit attractive to birds or whatnot to propagate its seeds high off the ground.

So, a tumbleweed strategy. The tumbleweeds are adapted to windy plains, and spread widely by shedding a ball (or bunch, whatever), of dead plant material, and let it be battered about by the wind, which slowly shakes out the seeds hidden inside and gives them a lot of spread. Obviously, our plant is in a forest, and has neither strong winds nor a flat plain - but the idea might be adapted. Maybe its seeds can be caught in a small, light bunch of dead twigs or shoots or even roots, which might be tossed to another tree by a breeze, or better yet grabbed by a bird for a nest. It will take a long time, of course, but the theory is sound. And the plant has some mobility and sensory capabilities, it might even be doing this on sort-of purpose eventually (sticking seeds on birds, or shaping twigs to carry them) after a while and quite a lot of selection towards activity (and sentience), of course.

Okay, now we have a parasitic plant mobile two ways! Actually, I think we're going to end up with tree sprites long before we get to ents, so bear with me. Mobility is expensive, so let's start putting that to work, not just the carnivorism. So, the plant, having adapted to tap into the host tree for water and minerals, will obviously want to stay on living material - if something is going on, if a branch is injured or sick, or even just the eating is better over that-a-way a little, the ability to move will be priceless. It can even move away from being eaten, or environmental hazards, or other sources of difficulty or injury, if it can move along the branch even a bit. Many parasitic plants propagate by runners and cuttings, with a long branch having the ability to put down new roots. If the old branch dries up and dies (to avoid overgrowing its host or its own abilities, or if the old spot stopped being viable), the plant can slowly, slowly, over months and years inch along branches to better feeding grounds.

Now, since our plant is a hemiparasite, it needs its host to be living. Trees with more active versions of our plant will therefore survive longer, since it will have fewer predatory insects damaging it with more coverage, and less of a parasitic burden on it with smaller plants - so more mobile versions will serve their trees best, and thus survive longer to continue to propagate. The tree may reward this behavior by developing nodes along the branches, around insect-areas, where the bark is thin to "encourage" the plant to root down here where more insects are, and after a time "dry up" the port where no insect damage is so that the plant keeps moving instead of overgrowing and demanding more resources. What tree is this? I don't even know, but it won't last forever, so go with it.

Mobile little plants, "racing" around their trees and munching on insects. We are actually getting there. With mobility and carnivority both encouraged, our plant has reason to continue along the path to better sensory capabilities, better mobility, and better reactionary capabilities... the same sorts of pressures that led to animals developing sentience, and eventually sapience in our humans. Whoo. In any case, now that we have mobile insect-munching plants, they will be sorta-competing with animal insectivores. Now, they won't ever be as quick as their animal counterparts, but what they can lean on is their plant heritage - they can tap directly into the tree, via rootlings, and take nourishment that way, and they can still photosynthesize for a bit more nourishment (encourage more leaf growth, perhaps, so they look more tree-ish - which is also camouflage). So to their advantage is multiple options, for when there aren't enough insects.

But the other thing they can develop, that will really help a lot? the ability to plan ahead. Especially since they will need to plan months ahead, to get things done (hey, this is sounding entish!). So, to go with their evolving sensory capabilities, they develop something like a neural network (can't be too specialized yet, since they are still moving by a grow-and-abandon strategy). This will let them react to stimuli more centrally, instead of just locally, let them correlate all sensory input and make moves based on that, and also lay the groundwork for future actual thinking capabilities.

So, being more mobile, and starting to be more capable of central, active decisions, our plant is adapting. One thing it will want, is to speed up and specialize its root system - tapping into branches where it pleases, where it wants to go, not just where it happens to land. At this point, if it had a tree species that adapted the node-system to nourish it and encourage mobility, it will no longer be necessary (though not abandoned, either - just that offspring can spread back to other species). Its leaves and even twigs might adapt to look more like it's tree, too, for camouflage, giving us "species" of ent later on.

We are into the home stretch, now. Recall that everything had to be decentralized, because our plant was going with a grow-and-abandon strategy of moving... well, the next step is to centralize. Instead of growing in a new direction and abandoning the growth placed elsewhere, the plant learns to "keep" and "re-purpose" a great deal of that effort - by losing less and less of the old growth until it is just abandoning the roots, and using its shiny mobility to "swing" the stems in the direction it wants to go, and put new roots down fast. Eventually, it may or may not reach the stage where it chooses short, spiked roots that can bite deep "quickly", and pull up without abandoning much of anything. Anyway, with this change comes the possibility of centralization. It can grow a node, where it can specialize sensory organs (animals evolved them, the attempts and failures would probably be recognizably parallel). It can centralize its reaction abilities, and decision making capabilities, into something vaguely analogous to a brain. It is still slow, it is still so very slow by animal standards - but now it can learn to speed up a little. It now has a lot more resources, since it isn't "abandoning" its leftover growth and starting new.

At this point, the plants will split into two populations (roughly. ish.) One sort will limit growth and continue to abandon overgrowth to stay small - recall, one of the reasons to be mobile was not to be too great a drain on the host tree by growing too large. Over time, they will develop first an instinct, then a culture, of protecting the mother-tree - since they are still far less mobile than animal insectivores, and their edge in competition against them encourages protecting and tending the host tree. Limiting their size will encourage the extra resources previously used for growth to be used elsewhere, letting them develop increasing mobility, speed, active defensive instincts, and eventually, some measure of intelligence (to animal levels, say). as small as they are, a tree may support many without strain - and being tribal (originally pack-oriented) will let them chase off larger dangers more efficiently, especially since they are still quite slow. Here are your tree sprites - small, lively, vicious in defense of their home-tree.

The other path, does not involve staying small. After all, it can move and react much faster than before, and adapt much quicker. In this variation, when the tree starts to show signs of weakness, from the burden of the growing plants - they jump trees. They will learn to root down quickly, to bite deep to take sap from a new tree, and to loosen their roots and move on when the tree falters. Moving from one tree to another lets them move on and stay alive even when they reach sizes that would be a burden to a single tree over time. They might stay with the same species (especially if they have developed a measure of camouflage), but they will quickly learn to move farther and farther, take bigger and bigger leaps, from branch to branch and tree to tree, even perhaps spanning and feeding from multiple trees at once when large enough. Once they're large enough, they will more precisely develop sturdier structural growth than they needed while small (from the woody stems of large vines, to something more like tree trunks themselves). Once they're large enough, and mobile enough, they might come down from the trees and move between them, at least long enough to get to a new tree to feed from.

Their instinct and culture will end up very different form the tree-sprites. Overlooking a number of trees will have them develop a more distant relationship - they won't develop the tree sprites' aggressive reliance on and devotion to their mother-tree, but they will care for the trees they feed from - tree herder, in truth - since that is their survival edge over their animal competitors (well, that and not being very edible except around the very edges). They will adapt to take on (or chase away) larger animals in defense of their trees, those that damage them, and even perhaps tear apart and eat them - they still are carnivorous plants. For that they would need to develop a larger mouth (mouth-flower, or something) for insects, the regular flowers will suffice. In any case, the more mobile they are, the fewer flowers they would have needed - since they are expensive to grow, and can move the flower to the prey instead of happening on it. This would have been part of the growth from flower-plant to treelike, I forgot to mention it earlier.

How big will they get? Not sure, but they will likely be quite spindly (to mimic branches), and can grow long and light because of it - and will probably keep growing most of their lives, until they are too big to support their needs or something else (injury, illness) kills them. Also, being plant based, might not need to support quite so much fleshy, squishy organs - long thin decentralized organs surrounded by structural growth will be better for their purposes. If their "feeding roots" come from the hands, they will be working with, not against, gravity for that part of their circulation system/feeding cycle. And they aren't likely to be "bipedal", so to speak, but to have several support structures (with no particular restriction on number) and be able to raise up to a height, probably on two "limbs" (kinda like bears) to reach up into their trees, so height when "standing" can be much greater than when otherwise moving. And given "several" limbs, people would likely try to equate them to something humanoid, to arms and legs, even if they might have five or six limbs, instead (though hub of sensory organs and nerve tissue will be "head" even if not very similar to our faces, people will still try). They may or may not mind minor parasites or flying plants (mosses or fungi), or might even cultivate them for some benefit - so there might be your "beards" or even "clothing".

But between the larger territory and the weaker connection to any individual tree, they will not develop as much possessive aggressiveness - instead, they will lean more on their hard-evolved planning ahead, allowing or even planning actions destructive to a single tree for the better growth of the whole area (or patch, or herd, whatever). Between that and the larger size, they are in a better position to eventually, eventually, develop something approaching sapience. They will be more likely to run into each other, being far more mobile, and need some language - and given they will not range far from their trees, a "taught" language will be more useful than an instinctive one, especially once they run into other "species" of ent (with different leaf-patterns and coloration, and thus a separation from the common ancestor at least from before tree sprites). It will be slow language, though, they are still living on plant time-scales. They can develop culture. And that, my friends, is how you grow an Ent.


The original ents were not so much humanoid trees but rather giants with a few vegetable traits that grew more prominent over time

Based on this definition, these ents could quite simply be regular giants that host a few symbiotic plants. Regular epiphytes could easily explain their branches and mossy coverings. Other traits, like bark or roots, need more justification

These traits could be explained as rather derived creepers, which can grow along the skin and produce bark, roots, and leaves adhering to the surface of the skin. Perhaps such plants could have roots to connect to the ent's blood supply, allowing such plants to be more incorporated into the ent's physiology

Another thing to add could be mycorrhizal fungi living in symbiosis with the ent, allowing the creepers and other plants to share nutrients and work entirely as a single organism


An ent should most properly look like a large willow tree in morphology. Many long, slender branches, each with many simply-shaped leaves.

Being able to manipulate each of these branches with a high degree of mobility, it maneuvers those and their leaves such that there is a "surface" presented to other non-ents. This surface can assume almost any shape (within reason) the ent might like. In many cases that shape is one of humanoid face or upper torso.

When it needs to become formidable, these shapes are inconvenient as each slender branch isn't really capable of lifting heavy objects or doing much beyond assuming the shapes described above. Instead, many of them gang together with their leaves folded back/inside, coiling into massive tendrils able to toss boulders or tear attackers into pieces. For legs, roots perform similarly.

A talented ent might even manage to shape "arms" and "legs" around those if merely trying to be intimidating, but in combat that performance might be dropped altogether, or shifted into something not very humanoid at all (a monster whose shape keeps shifting between gigantic predators and mouths with chainsaw teeth roiling around). Weapons could be useless, as you fire arrows into it, only to tear a few leaves. A giant "boot" comes down on an ally, covering him completely. Inside of it, tendrils slowly strangle him, but to a somewhat distant observer it might appear that he has been squished flat (assuming ents have never bothered to give away the secret that their "shape" is mostly hollow).


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