Grafting & Growth: On Trees as Infrastructure

The cultural and ecological ingenuity of trees: from living bridges and clothing to natural air conditioners.

When thinking about fantastical worlds, I tend to divide the ecosystem into two main types: the chaotic, and the straightforward.

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, which is not to say less rich —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.

In either system, a potential component I think tends to be tragically undervalued is trees.

Trees are remarkably versatile.

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.

Ecologically, trees anchor ecosystems profoundly. Wolf trees serve as critical hubs, connecting seedlings through subterranean fungal networks and root grafts, sharing vital resources. The swollen-thorn acacia has a symbiotic relationship with ants, offering shelter and nectar in exchange for protection from herbivores. Coastal redwoods—Earth’s tallest trees—support entire ecosystems within their immense canopies, nurturing unique birds and mammals high above the ground. The Montezuma Cypress has a circumference of 119 feet, which is roughly twice the size of the average American living room. Mangroves use aerial roots with lenticels to stabilize soft soils and breathe oxygen in flooded environments.

Trees bridge societies culturally and literally.

In India, living tree bridges made from the aerial roots of rubber fig trees roots offer centuries of durability, creating functional ecosystems. Redwood giants are large enough to physically span roads—literal bridges and perhaps imaginative, interdimensional ones like Jack’s beanstalk or the World Tree Yggdrasil.

Below ground, root grafts and fungal associations connect into vast subterranean networks. Old trees serve as critical hubs, sharing resources with younger trees.

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: tamarisk trees¹ — mentioned in the Bible, the Iliad, the Shahnameh, and the Epic of Gilgamesh — function as natural air conditioners, 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 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, ghost forests offer powerful imagery about how sudden catastrophes can destroy whole ecosystems. The cedars on the banks of the Copalis River, near the Washington coast, died simultaneously in 1699. An earthquake had caused the land to drop — which killed the cedars. They are spread out across a low salt marsh on a wide northern bend in the river, long dead but still standing. Leafless, branchless, barkless, they are reduced to their trunks and worn to a smooth silver-gray — a visual I’ve associated more strongly with birch, historically.

Ironically, wood is a popular building material in Japan because of its earthquake resistance. 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, or the schmoo popularized by the amazing movie Lucky Number Slevin 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. Treated wood is also incredibly long-lasting; cedar was a vital shipbuilding material for millennia.

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 ents², to Groot of Guardians of the Galaxy fame—riff off 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.

Metaphors from literature often use trees to discuss growth and healing.

Naomi Novik, in Uprooted, writes, “A tree isn’t a woman; it scatters seeds widely, hoping some might grow,” echoing hopeful growth. Elizabeth Moon uses tree scars metaphorically in Paksenarrion, offering a reminder that injuries heal but shape identity forever.

We can grow no cherries on an oak, nor acorns on a holly. And however your life goes, Paksenarrion, it cannot return to past times: you will never be just as you were. What has hurt you will leave scars. But as a tree that is hacked and torn, if it lives, will be the same tree—will be an oak if an oak it was before—so you are still Paksenarrion. All your past is within you, good and bad alike.

Moon is right; there’s a limit to how much you can force a tree to bear unnatural fruits. But you can grow cherries on an apricot tree; the tree of 40 fruits is one of my favorite art projects. And grafting comes up in magical contexts in fantasy novels a fair bit, typically as a metaphor for some Frankensteinian grotesque — which I think is a shame. Grafting is a beautiful thing.

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 from in the Mario Bros. franchise.

Trees make for great obstacles in storytelling.

Osage-orange trees evolved thorns to deter extinct megafauna; such traits persist despite the extinction of the original threats, a fun evolutionary echo. Phenotypic plasticity allows trees to develop curly or prickly leaves as defense against herbivores—which may have been the original inspiration for whimsical foliage like Dr. Seuss’s trufula trees, source of the multipurpose thneed. 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.

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 Grimm³, 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.

A fantastical tree, as central to a created culture as Dune’s sandworms, could 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.

Further Reading

• Moss and Fog has a beautiful collection of photos of remarkable trees throughout the world.

1. Since they're very salt-tolerant, tamarisk trees are the only trees found on the shores of the Dead Sea. There is a Persian epic poem that involves an otherwise invincible Prince, Esfandiar, who can only be wounded by a tamarisk arrow to the eye. It's really similar to stories like Baldur and the mistletoe or Achilles’ heel. A different famous piece of Babylonian literature involves an argument between a date palm and a tamarisk, planted beside each other in a king's garden. At one point, the palm makes fun of the tamarisk for being used as a trash can.

2. Speaking of ents and Groot, did you know bananas can walk? Bananas are not actual trees; they are considered the world’s largest herb. What is commonly mistaken for a trunk is actually a pseudo-stem made up of tightly packed leaf bases. But they’re said to “walk” due to their unique way of growing. As new growth develops, the plant can “move” slightly from its original position as new shoots emerge from the base, giving the impression of a gradual shift. Hardly anthropomorphic, but interesting.

3. I visited the Black Forest back in 2019 when I was pregnant with my son; it was the first time I felt like I understood German fairy tales on a visceral level. Pine barrens are different from oak forests are different from cypress swamps — if you’ve only ever been in one biome your whole life, it can be difficult to intuitively grasp how the psychology of a place can inform local culture and its stories.