Some trees are wise, but sometimes they aren't smart enough. At least, alone. With a forest, these trees can act as a sort of neural network, creating a collective consciousness. An arboreal brain. Plants have roots, and roots kind of look like neurons, so perhaps that comparison is why the idea of a sentient forest is a thing.
These neural roots can be considered both a Genius Loci and Hive Mind, being both a sentient location and a meld of hundreds or thousands of individual minds. It might explain why the jungle or forest is trying to kill you; the whole thing's an intelligent environment and doesn't take kindly to trespassers. This also often overlaps with Enchanted Forest, and especially in fantasy works it's common for sufficiently ancient and primordial woodlands to become genii locorum as a result of the density of magic seeping into their wood and soil. If such a forest is home to Nature Spirits, Plant People, Treants, or similar beings, it will often be able to rouse, direct, or communicate with them if they are not simply extensions of its mind. If it's just a single intelligent tree, its a Wise Tree.
Examples:
- One Piece: During the Whole Cake Island arc, Luffy and half of his crew travel to Totto Land, the kingdom ruled by its queen and one of the Four Emperors, Big Mom. Within her territory, it is known to be populated by animate inanimate objects created by her Devil Fruit, and looks straight out of a fairy tale. Whole Cake Island itself has the "Seducing Woods", where the trees are alive and can talk like people. Like many things about Totto Land, however, the Woods use a whimsical charm to mask a dark and twisted nature. The trees can uproot themselves and change their position to disorient intruders and leave them vulnerable to either being totally lost or being taken out by one of Big Mom's crew that's sent to attack them.
- Equestria Divided: The Everfree Forest possesses an awareness and will of its own, which ponies can nurture a bond with to develop magical powers and which can move the wilderness' plants and creatures to its own defense.
- Avatar: Eywa, Pandora's global consciousness, is described as a vast network of fibre optic-like branches and roots. The Na'vi can hook themselves into this network and upload or download information.
- The Divine Comedy: Dante and Virgil visit the Wood of Suicides, a forest made up of sentient trees. It turns out they're all human beings who were turned into trees for committing suicide.
- Double Vision, by Tricia Sullivan, has the Grid, a seemingly sentient fungal clonal colony on an alien planet. It turns out that it's the main character's subconscious attempting to interpret TV marketing.
- Federation of the Hub: In "Balanced Ecology", the diamondwood forest on Wrake is a closely integrated ecology with, as it turns out, its own plans for how to cope with the human colonists on its world.
- Alan Dean Foster:
- Humanx Commonwealth: In Midworld and Mid-Flinx, the green world with no name is effectively this trope, all of its vegetation being linked as a gestalt consciousness. They-Who-Keep, a type of tree in which the human inhabitants entomb their dead, form this global "nervous system's" most crucial "ganglia". It's later shown in a short story that the plants don't even need to be in physical contact when the forest has a conversation with the AI on Flinx's ship about the ethics of forcing Flinx to go save the universe via mind control vs just trying to nudge him into making that decision on his own through the plants he was given as gifts before leaving the world. It Makes Just As Much Sense In Context.
- Spellsinger: While not necessarily intelligent, but there's a communal plant-creature in The Hour of the Gate that moves slowly through the Swordsward, through the coordinated movements of hundreds of interwoven plants. Definitely some sort of neural-analogue communication at work there.
- Hainish: Vaster Than Empires and More Slow features a group of astronauts coming upon a planet devoid of animal life but covered by a global forest, from which intense fear can be felt emanating. The astronauts eventually realize that the forest itself functions like a tremendously vast mind, and the fear they felt was the world-forest's apprehension at encountering other thinking beings for the first time after a long, long life in isolation.
- Ki Kiwi: The forest is said to be able to think, but the trees themselves seem like normal trees.
- The Kingdom Beyond the Waves: The Daggish is a region of the Liongeli Jungle which operates as a Hive Mind, assimilating plants, animals, and unlucky explorers into its consciousness. It's a result of one of Camlantis's Organic Technology waste-processing sentient trees, left behind when the city was launched into the sky, mutating over the intervening millenia and exploiting a mind-control artifact.
- The Lord of the Rings:
- The Old Forest is something like this, and alongside Fangorn Forest is a remnant of a massive, ancient forest that once covered most of Western Middle-earth in the First and Second Ages. The trees by themselves don't appear to be completely sapient (although Old Man Willow comes closest), but they all work together to funnel intruders deeper into the forest. They're also described as having their own strange thoughts and emotions, as well as something of a hierarchy, with the oldest trees influencing the others.
- Fangorn Forest on the other side of the Misty Mountains is, like the Old Forest, a remnant of a massive ancient forest, and is populated by a combination of Ents, regular trees, Ents that have become tree-like, and Huorns — sentient, mobile trees that the Ents have woken up. Old Man Willow itself is strongly implied by Treebeard to be a malevolent Huorn.
- Muddle Earth (Stewart): Elfwood, the forest surrounding Giggle Glade where Dr Cuddles dwells, is a forest which is full of talking trees (since the novel is a parody of The Lord of the Rings, this would likely make them an allusion to Fangorn Forest). Needless to say, they're not especially on board with him cutting down their numbers to build a giant Trojan tree-rabbit.
- Rust and Humus: The trees of the age of the humus are interconnected by their webs of roots, granting the global forest sufficient awareness and intelligence to impose its desires on the beings living within it.
- Semiosis: Stevland the Plant Alien is a colony of bamboo-like plants that spans miles, sharing a single root system. He's sapient and has great control over his own biology, enabling feats like growing new sensory organs and temporarily partitioning some of his mind in one of his groves.
- Speaker for the Dead: The trees on Lusitania, although each one is intelligent, are host to a more powerful entity collectively.
- Star Wars Expanded Universe: Bafforr trees used roots to create a surface-wide forest brain on Ithor.
- In Galaxy of Fear, Tash craves connection with something larger than herself, as her Force powers are weak and untrained and can only rarely give her that feeling of oneness. She briefly manages on Ithor, when the bafforr forests help her out.
- Smaller collections of these trees can also be intelligent with a distinct mind, but there have to be enough of them. Momaw, the Ithorian in Tales from the Mos Eisley Cantina kept a tiny grove alive in an underground chamber on Tatooine. When an Imperial enemy killed one, the remainder were not quite sapient enough to comprehend the situation and advise Momaw.
- The Tough Guide to Fantasyland: In some Woods, the entire forest — plants, animals, the whole lot — is an intelligent entity, usually directed by an immense, ancient tree in its very heart. It does not like intruders, and will try to kill them or at least get them lost and let them starve. The only way out is to communicate with the wood and get it trust you, which can earn the travelers some profound wisdom.
- Uprooted: The Wood is presented as a darkly intelligent force, fully aware of itself and its surroundings and capable of patient, complex and highly intelligent planning, and motivated by active hatred for humanity. In the end, it's shown that this isn't actually what's going on — the Wood is by nature just a regular if magical forest, but is being controlled by the will of an individual being.
- The Vorrh: The trilogy's eponymous Genius Loci is an ambiguously benevolent one. It was created by God at the beginning of time and houses the Garden of Eden, and spending too long inside can turn one into a mindless pseudo-zombie called a "limboia".
- Power Rangers Cosmic Fury: Levvina is a planet covered in a forest where all the plants are part of the same mind. It instinctively ensnares people who trample on the vegetation and puts Aiyon through some slapstick when he tries to pick its fruit. Still, it's a benign entity, saving Zayto when he crash lands on its surface.
- Exalted: As is the case with several other locations there, most of the forests within Malfeas are living, intelligent entities in the own right.
- Szoreny, the Silver Forest, is one of the Yozi themselves — strictly speaking he's actually The World Tree, but he was buried upside-down by the Exalted when the Yozi were defeated and his roots now form a vast forest. He's just as fully aware of what goes on within his expanse as the other Yozi, and permits hunting parties to operate within him provided that he's offered prayer and sacrifice beforehand.
- Hrostivtha, the Spawning Forest, a soul of the Yozi Isidoros in the form of a forest of living brass. It represents Isidoros' lusts and primal instincts, and causes those who enter its bounds to feel a strong mixture of arousal and violent urges. It's populated by a variety of monsters and creatures, some brought to serve as quarries for hunts and some born to the forest itself.
- Mursilis, the Skittering Jungle, is a soul of the Yozi Oramus that represents its desire for freedom from its imprisonment. It's composed of and populated by immense, constantly shifting swarms of metallic insects — its trees are either giant mantis-like things or swarms of smaller insects in the shape of trees. Some are its component souls and their progeny, but most are part of the vast Hive Mind that makes up the living forest itself. It's known to rearrange its shape and even move location entirely on occasion, with the entire mass of the forest migrating to a new spot and devouring everything in its way.
- Zannanza, the Sideways Forest, is a borderline example. Rather than being a living collection of trees in the strict sense of the term, she's a giant fleshy monster with a forest growing from her back.
- Magic: The Gathering: Dominarian forests have maro-spirits, entities who are empathically and spiritually linked with every tree and living creature in the forest and act as a living representation of the forest's soul.
- Numenera: Trytherhon is a parallel world covered by a global forest of sapient trees known as the Elders, which are joined through their extensive root systems in a shared dream that unites the entire forest in a hazy, connected awareness.
- Warhammer: Athel Loren, the forest where the Wood Elves live, is so thoroughly steeped in magic that it's a living, aware thing in its own right, and to some degree is conscious of everything that goes on beneath its canopy. While the Wood Elves are themselves fully capable of defending their home from intrusions, Athel Loren itself actively fights back against attacks, twisting paths, moving trees and directing dryads, treemen and forest dragons to its defense.
- Against the Storm: The forest is at least semi-intelligent and always aware of your settlements and actions, and in particular hates woodcutters and glades being discovered while also fearing the fire that burns in hearths. The longer a settlement lasts, the more the forest's Hostility grows and the worse the storm gets on settlers as a result.
The forest always watches.
- Darkwood: The titular forest is more like a mass of alien vegetation which has overtaken a large swath of land in 1980s Poland, and several characters make reference to the woods being "alive" or speaking to them. The end of the game reveals that the forest and all the mutated creatures within it are shoddy, alien imitations made out of biomass by an otherworld entity called the Being that lives underneath the surface of the area.
- Mass Effect 1: The Thorian in the first game is a sentient plant-like thing. As researchers in-game commented, no-one really knows what to classify it as. At first they thought there were a bunch of plants along the surface of the planet, but later they realized it was just one big plant.
- Pajama Sam: Many of the trees, like so many other "inanimate" objects in the Land of Darkness, have faces and personalities of their own. During his travels, Sam runs into not one but two forests of sapient trees, neither of them particularly friendly. The first performs a rather aggressive customs check and relieves Sam of the equipment he needs to confront Darkness, while the second straight-up refuses to let Sam pass because he's not a tree (nothing a Bark-Thin Disguise can't take care of, though).
- Pokémon: Trevenant, a Ghost-type created for a deceased human soul possessing a tree, can control the trees of the forests it inhabits by connecting its roots to theirs to form a kind of nervous system.
- Sid Meier's Alpha Centauri: The Xenofungus serves as a hindrance to terraforming and a hiding place for the rapacious Mind Worms. It also turns out to be a vestigial neural network housing a fledgling sentience, one which has achieved near-godhood on multiple occasions in Planet's history only to inadvertently trigger mass extinctions which resulted in its inevitable collapse. The human factions can not only aid the Planetmind in its ascension, but use it to achieve their own transhuman evolution.
- Stellaris:
- In the "Migrating Forests" event chain, the colony world's mobile forests are discovered to possess a form of rudimentary communal intelligence, allowing them to choose where to move, respond to new developements, and form opinions of other beings. If the peaceful study and coexistence route is taken, they acclimate themselves to the colonists' presence enough so as to consciously avoid their settlements as they wander around, while if you choose to firebomb the forests the survivors will retreat to recover before counterattacking.
- The Ancient Relics DLC has the Baol, an ancient race of plantoid Precursors. At their height, the Baol were spread out over much of the galaxy. Each individual world counted as an Intelligent Forest in and of itself, and all of them were linked together into one vast hive consciousness.
- Submerged: Hidden Depths: The Mass is an underwater variant: a sprawling network of vegetative tendrils that extend throughout the sunken city. Although its intelligence may be too alien for proper communication, it's self-aware enough to solicit Miku's help via its "gift", and to brutally avenge the theft and torture of its Seeds.
- The Trader of Stories: The forest is not just intelligent but outright snarky, being made of crotchety old trees and younger trees that care for saplings. The main character (a human) is only tolerated by some of the trees and accepted by others, which is why she eventually leaves.
- Tsukihime: One of the twenty-seven Dead Apostle Ancestors is a forest that absorbed the blood of an Ancestor that Arcueid killed. It was named after the former Ancestor and became known as the "Forest of Einnashe". The forest gained sapience and mobility, wandering around, swallowing entire towns and tempting people to enter it with rumors of an immortality-giving fruit tree.
- In Kevin & Kell, the tree that Lindesfarne and Fenton live in has mentioned that all plant life can communicate via an interconnected root system
. Apparently, it somehow works for potted plants
as well.
- Nixvir: Parts of the Twilit Forest of Drache are sentient, as Oriel is seen asking for directions from sentient trees, one of whom babbles about not being able to cope and "hurting" (a nod to Dante's wood of suicides).
- Avatar: The Last Airbender: The Foggy Swamp is a huge habitat in the southwestern Earth Kingdom reportedly made from one central tree. The "forest" itself seems to have a mind of its own, too, although whether it's sentient or not is mysterious.
- The Magic School Bus Rides Again: The students are temporarily transformed into an example in an episode about trees' interconnections with fungal mycorrhizae, as discussed under Real Life below.
- Totally Spies!: In "Nature Nightmare", the spies have to fight the Mad Scientist Lasputin Zero, who has made trees intelligent in order to protect them from humanity, creating an entire forest of them. They go out of control however, and plan to attack innocent people. The Spies eventually stop the trees by destroying the queen tree.
- A limited version of this occurs in real-life plants through mycorrhizae
, fungi that live in symbiosis with plants, usually trees, by growing into their roots and helping them extract nutrients from the soil in exchange for sugar produced from the plants' photosynthesis. An individual fungus' underground network of hyphae can grow very large and connect to multiple trees at once, allowing groves or entire forests of suitable trees to become interconnected with one another. These fungi can act as relay networks for the plants' chemical signals, allowing them to "communicate" with one another — for instance, a plant attacked by parasites or herbivores will send warning chemicals through this system, which will prompt connected plants to produce toxins or release chemicals to attract predatory animals.

