Summary

This is a fork of (Treez - Automated Tree Planting by idisssnakes) that has taken on a life of it's own. This port makes it not rely upon space age and SE compatible.

Main gameplay loop

Cut down trees, craft seeds, plant them and wait. Trees will grow from seeds over time (during the day) and higher levels of pollution slows tree growth rates down. Research saplings to improve the number of trees you can grow at one time.
Fertilizer crystals (they work only at night) which can improve soil quality (just visual benefits). Fertilizer will initially pollute while placed but can be reduced with research. This is the tool you want to use if you want to actively improve soil quality. Repeated applications are required.

What's the winning strategy with Treez?

Grow small groves to start. As you unlock research more you can grow more trees simultaneously.
Plan your factory in blocks or chunks but don't activate them yet. Plant seeds in all the extra spaces you want/can. Wait for the trees to grow before activating it. Or alternatively have a pollution sensor detect if the pollution threshold of that chunk is above threshold X, turn that block off.
One key self-balancing point is trees will take damage while absorbing pollution (obvious if they are alone). But if they are in large groves, the grove absorbs pollution without trees taking damage. So you want the 'right' amount of trees for the right amount of pollution you are generating in that chunk. ~17 trees per 1 point of pollution absorbed.

Console Commands

/treez - Debugging information
/treez fix-sites - Fix any placed seeds sites and turns them into waiting seeds in queue
/treez force_nitrate - Trigger any nitrate pellets which have not yet triggered. Useful for debugging and testing.

External Mod support

Has Alien Biomes, dynamic rain, terrain evolution and space-exploration specific hooks.

For dynamic rain - trees grow faster in rain. Rain might plant seeds or drop nitrate crystals to improve soil health.
If terrain evolution 2 AND alien biomes are enabled, this will provide a decay pass for alien biomes.
Alien biomes - Nitrate pellets will restore soil per the tiles in alien biomes.
Space exploration - blocks seeds and nitrate pellets from being placed on spaceship floor tiles, asteroids, etc...

Other mods it pairs well with:

Dynamic Rain for multiple hooks for planting seeds and nitrate.
Dirty Launches for mass wide-spread pollution. Gives you a reason to plant trees.
Pollution: Impactful Smog really showcases the pollution impact on your base. Trees will improve visibility with this.
Pollution Smoke makes it obvious where your main polluters are. Might want to put trees near there.
Pollution is the Solution encourages a wide area pollution area, this gives you a tool to control your spread.
Terrain Evolution 2 destroyes your biomes if you let the pollution get too bad. So it encourages you to plant more trees and use nitrate pellets to revitalize the planet. Or maybe having a desert wastland is a reason to expand the factory. :)
Desirable Dirt Paths is another terrain modification mod.
MiningScars by Mylon gives you another reason to restore the planet.
Pollution Combinator to cut power to buildings to curb pollution to levels your forests can manage.
Tree Healing to help repair any tree damage.