This is a trope, mainly in science fiction, where a ship or vessel of some kind is literally made out of a tree. Not merely made out of wood, or that a tree was used in the construction, this ship actually looks like (and possibly functions as) a giant tree. A key element is that the tree should be living, and was grown/created/transplanted specifically for the purpose.
Most often used in Science Fiction, though not necessarily limited to it. In certain cases it may be used to show a race as basically Space Elves who have both high technology and still are in tune with nature.
- Sailor Moon: The Makaiju ("Doom Tree" in the American dub) was originally a tree on an alien planet. When the planet was destroyed, it uprooted itself and proceeded to travel through space, sheltering some of the inhabitants of the planet in its roots.
- Tenchi Muyo!: Juraian ships are all sapient, giant trees that are shaped to look and function like spaceships. This also means that after being shot down, they can be regrown as long as the core tree survived.
- Saga: There's an entire forest of rocketship trees, and they don't die once they've blasted off. They're very much alive as they travel through space, and seemingly fond of their passengers.
- Animorphs: Pemalite ships use huge trees as computers for their spaceships. Even Ax (whose species' ships have giant biodomes filled with forests and plains) finds it ridiculous.
- Genesis Quest and Second Genesis involve travelling in heavily engineered spacegoing Poplar trees that use reflective leaves as solar sails, and whose trunk holds air spaces.
- Hyperion Cantos: The Ouster "Treeships", which are built around a single, massive living tree made vacuum-sealed and spaceworthy by containment fields.
- The Last Continent does this with a tree that's been made into a boat by the local god of evolution. The sail is a leaf, the hull is a floating seed, etc.
- Revelation Space Series: The "Greenfly" infestation that is taking over the galaxy in Absolution Gap is shown to be billions of self-contained biospheres containing trees and tree-like plants.
- Xeelee Sequence: In Raft, one of the strange lifeforms in the high-gravity universe is a species of mobile floating trees. Humans turn them into vessels and steer them through space.
- Dungeons & Dragons: Space vessels created by elves in Spelljammer are grown, not built, from living, leafy trees.
- Starfinder: Xenowarden ships are seamless mixes of technology and plant life that are grown as much as built.
- The most common models are modular, podlike ships shrouded in large leaves that act as solar panels and armed with spore pod launchers. The largest, rarest capital ships are essentially spaceworthy forests, with numerous titanic trees anchored around a technological core and protected by force fields from the hard vacuum of space.
- On the one hand, these ships are remarkably self-sufficient, as they run almost entirely on solar power and can produce enough oxygen and hydroponic food to sustain their crews indefinitely. On the other, their organic makeup makes them very vulnerable to radiation-based weaponry.
- Orion's Arm
- "Dyson Trees" are genetically engineered giant plants that can survive in vacuum and synthesizes nutrients from ices found in a comets or icy asteroids, into which they're rooted, and can grow into vast orbital habitats. Inside their trunks and larger branches there are sealed hollows filled with air, inside which other lifeforms — like humans — can live, while their spherical canopies support further air- and water-filled habitats, as well as space-adapted lifeforms.
- Spacecraft like this are mentioned as being used by the Eh'ern, furry, egg-shaped aliens from an arboreal planet in the Triangulum Galaxy. They're an ancestrally arboreal species and primarily live in space-adapted derivatives of their homeworld's arboreal plants, similar to much larger Dyson trees, which they sometimes outfit with reactionless drives to turn into immense, interstellar ships.