Trees and forests have captured our imaginations for millennia. From the sacred groves of the Celts to Tolkien’s elves, Phoenician cedar to the Black Forest of the Brothers Grimm, trees play an enormous role in real-life cosmology. They also have tons of untapped potential when it comes to being useful for fictional characters and societies.
The world tree is a vital part of the cosmology of many cultures. Typically, its branches extend into the heavens, its roots provide passage to the underworld, and the trunk allows for travel between the mortal realms and the realms beyond. The Hungarian világfa permits shamans to climb into the layers of the sky, into heaven and hell; its branches house the sun and the moon. The sacred asvattha is described in Hindu scripture as eternal, its roots spread upwards, its branches pointing downwards, having neither beginning nor end. World trees play an important role in Mesoamerican cosmology and are depicted extensively in Mesoamerican art. Northern Asia, too, has its myriad of world tree myths.
Throughout human history, throughout the world, trees have been sacred and central to our understanding of the world. The World Tree. The Tree of Life. The Tree of Knowledge. Warden trees. Wish-fulfilling trees. Although most of the advancement of Western civilization has involved clearing trees rather than cultivating them, trees and their products have been as important as stone or metal throughout human history. Wood rarely makes its way into the archaeological record, but humanity would have had a difficult time advancing without trees, which provide timber for building homes and ships, fruits and nuts to feed us, and even the oxygen we breathe.
Our truly fantastic fiction rarely reflects the role of trees in real life cosmology. Discworld rests on the back of a turtle, and even Marvel’s Thor concerns itself more with the Bifrost Bridge than Yggdrasil.
When creating a fictional world that is not Earth, whatever genre, there are two main paths to take. The first mirrors Anne McCaffrey’s Pern series, which has its complex ecosystem replete with all manner of invented organisms, from painkilling juices to empathic lizards to ravenous fungi. Although the dragons of Pern are key components of the storytelling, they are not a part of the food web that defines needlethorns or dolphins. L. E. Modesitt typically takes this approach with the sentient, magical soarers of the Corean Chronicles largely unconnected to the herder’s nightsheep or military’s pteridons. Works modeled off folklore and myth, such as the Garrett, P.I. series by Glen Cook, often go this route. This approach is also true for riffs off of tabletop gaming, like Nightseer by Laurell K. Hamilton or most works by T. Kingfisher.
The other, more common—less complicated—method is to center worldbuilding around one primary component. In the case of Dune by Frank Herbert, its sandworms, spice, and the planet’s extreme desertification result from the sandworm life cycle. Robin Hobb’s dragons were critical to every aspect of the ecosystem of the Realm of the Elderlings; from the acid-waters to the ship’s timbers, everything traces back to the dragons.
Imagine a tree as firmly integrated into a world as the great reptiles that more commonly capture our imaginations. The Celts had their sacred groves; though this sort of reverence is associated with elves in fantasy fiction; from Tolkien’s Lothlórien to the fae curse “oak and ash” invoked by Seanan McGuire’s October Daye, authors need not feel so limited.
Most people know that trees (like all plants capable of photosynthesis) function as air purifiers, taking in carbon dioxide and outputting oxygen. Dyson trees (genetically engineered plants designed to live inside of comets) and their ilk have been a staple of space-based science fiction as a way to facilitate asteroid habitats and generation ships for decades. In the same vein, trees provide vital access to heat in pre-industrial societies, via combustion and burning. But trees can actually do so much more: the Middle Eastern tamarisk tree functions as a natural air conditioner, cooling the surrounding air not just by shade, but by secreting salt during the day that then absorbs water from the air overnight. As the water evaporates, the surrounding air cools.
Of course trees provide food as well as air; apples, oranges, dates, almonds, olives, and coconuts are all well-known examples of produce. Reality takes things a step farther. For example: acorns are readily ground into usable flour, no wheat needed. The sap of palm trees is self-fermenting, resulting in a tasty and very popular wine that is very popular but unfortunately not shelf-stable enough to be appreciated by most of the west. Sassafras teas and root beers are also tree products that could be enjoyed in lieu of the teas and coffees that typically appear in fiction.
From a liquids perspective, trees can purify water in a variety of ways. The image of a stranded seafarer surviving off coconut milk is iconic, but modern aerogels let authors take this a step farther. Some aerogel varieties take their inspiration from trees, using capillary action to push dirty water upwards for the sun to evaporate, which produces steam that can be siphoned off as fresh, clean, potable water in emergencies. Similar mechanisms could be used in science fiction or fantasy settings, with characters using trees as filtration systems.
Speaking of emergencies, despite our modern biases, trees provide an excellent building material. Popular in Japan because of its earthquake resistance, treated wood is incredibly long-lasting, and cedar was a vital shipbuilding material for millennia.
It need not just be elves who make their homes in trees; the protagonists of Bill Holbrook’s long-running webcomic, Kevin & Kell, live in massive trees. Redwood trees, enormous enough to dwarf even the largest of humans and their vehicles, prove that it is possible for trees to make viable bridges (whether in their capacity as an interdimensional world tree or not!) and span roads. As with Dr. Seuss’s thneed, the possibilities are endless.
Tree-based clothes aren’t just reserved for The Lorax, either—nor exclusive to the metaphorical fig leaf of Biblical Eden. The people of the Niger-Congo region of Africa have made cloth out of bark for thousands of years; though it predates weaving, it is still worn in Uganda and, when left undyed, has a beautiful terracotta hue. Chinese silk would have been impossible without mulberry trees, and nuts like walnuts and acorns are incredibly useful for tanning leather and dyeing cloth. The oils of trees like cedar can be used to preserve textiles as well, acting as a repellent to insects that might otherwise destroy natural cloths.
But what about the magic? In some versions of lore, vampires can only be killed with wooden stakes—occasionally, only stakes of a particular type of wood. Dryads and other spirits sometimes inhabit trees, either symbiotically or as a single being. Sentient trees—ranging in intelligence from telepathic trees of Avatar’s Pandora (which is leveraged by recent research into plant communication), to Tolkien’s ents, to Groot of Guardians of the Galaxy fame—riff off of this mythological trope. Folklore also brings us trees, like the Juniper Tree, that house the spirits of the dead and allow them a “body” from which to act. Naomi Novik uses this device to great effect in Spinning Silver, for example when the protagonist Wanda prays to the mystical white tree where her mother was buried for help—and subtly receives it.
Trees, being biological constructs, are effective biological agents, which means they can affect human health. Narcotic effects are common, for example the G’Quan Eth of Babylon 5 or Pern’s fellis juice; obvious expansions on folk remedies include willow bark tea. Larry Niven takes the idea of tree-as-medicine an enormous leap forward in his Known Space series—the Tree-of-Life (actually a bush resembling a yam) houses a symbiotic virus that triggers incredible metamorphosis in hominids, making them stronger, smarter, and functionally immortal. Niven’s Ringworld also brings us “slaver sunflowers,” which function as solar-powered lasers able to target intruders with powerful beams of light, similar to the fire flowers faced in the Mario Bros. franchise.
Trees make for great obstacles in storytelling. The Whomping Willow of Hogwarts trapped Remus Lupin in his werewolf state and served as a guard of an important secret passage into the nearby town of Hogsmeade. Even without adding fiction to the mix of science, wildfires are an incredible danger, as shown by Janet Kagan’s Mirabille—but Hyperion's Tesla Trees take it a step farther by accumulating enormous amounts of electric charge in their onion-like bulbs, which they can then discharge into the Flame Forests.
In Your World
Imagine a fantastical tree, central to a created culture, that can do it all. A tree that could facilitate travel between communities and dimensions, like Jack’s beanstalk or the World Tree. Imagine that its base could house its caretakers, its bark and leaves clothing its caretakers. Its very cells could purify the air they breathe, perhaps rendering an otherwise hostile environment, like space or a magical dimension, livable.
Such a tree might provide food, in the form of nuts, berries, or even the fleshy pulp, and drink as well. A root tea that purifies the water it touches even more thoroughly than boiling is not inconceivable. Such a tree might offer danger and salvation, inspiration and comfort. It would doubtless play a key role in the cosmology of that society’s people, whether it be large or tall, deciduous or winter-green, jealous of its space or cloned and grove-born.
Note: There are a couple of affiliate links & codes scattered around, but these always come from links I was already recommending and usually I share them because they benefit you too (i.e. getting you extra time on trials).