Tree Regrowth & Saplings
Forests come back. Trees slowly spread onto nearby natural ground, chopped trees drop saplings you can replant anywhere, and a tree ringed with concrete stays put forever as a single decorative tree.
Features
Forests spread on their own. Living trees occasionally seed a new tree of the same species a few tiles away — onto natural terrain only (grass, dirt, sand). A density cap makes forests creep outward at their edges instead of thickening into solid walls.
Saplings from logging. Mining a living tree has a 25% chance to also drop a tree sapling, right from the start. Researching the cheap Forestry technology (25 automation science) then unlocks crafting saplings from 2 wood — so early on you transplant what nature gives you, and later you can reforest at scale. Both are configurable.
Plant anywhere natural. A placed sapling grows into the dominant tree species within 16 tiles, so replanting a clear-cut area restores the local forest type. With no trees nearby it becomes the classic green tree — perfect for founding a new grove that then spreads on its own.
Blueprint your gardens. Saplings are real buildable items, so tree arrangements can be blueprinted and planted by construction robots.
Decorative single trees. Spreading never crosses player-placed tiles. Pave around a tree with concrete, stone brick, or refined concrete and it stays exactly where it is — one tree, forever.
Plays nice with the world. Spreading skips polluted ground by default, dead and dry trees never propagate, and modded trees are supported — they drop saplings and spread too.
How it works
Every 5 seconds the mod tests a handful of random already-generated map locations per surface. Where living trees exist, one may seed a new tree nearby if the ground is natural, unpolluted, unobstructed, and not already dense with trees. The checks are cheap and bounded, so the UPS impact is negligible even on large maps.
Settings
Everything is tunable in Settings → Mod settings: sapling drop chance, crafting recipe on/off, spread rate and distance, forest density cap, pollution blocking, and species matching.
Compatibility
Factorio 2.0+, with or without Space Age.
Space Age's agricultural tree seeds are a separate late-game system and are untouched. This mod is about the world's forests, not wood farming — though saplings do make wood renewable early; disable the crafting recipe if that feels too generous.
Safe to add to an existing save. Also safe to remove: every tree this mod plants is a vanilla (or other-mod) tree, so uninstalling leaves your forests exactly as they are — only the sapling items disappear.