I've spent the last few weeks working on a new procedural tree generator. Same six parameters as before: age, surface gravity, apparent solar luminosity, moisture, solar spectrum/peak wavelength, and average global temperature. They interact to affect the shape, size and color of the trees, as well as the effective age/evolutionary progress of the biosphere.
Planets with a low effective age are covered in moss/algae. A high effective age yields trees. There's an "age of ferns" in a sweet-spot between them, just after the evolution of vascular plants but before woody tissue, where clumps of fungus of varying shapes (eight modeled, all very simple) also grow.
Here is an Earth-like planet.
6x gravity. Stout trees.
This tiny planet's trees are stupid tall (as opposed to dummy thicc).
Old, cold, covered in mold.
There are improvements that can be made, particularly with moss and ferngus generation, variety of leaf shapes, branch shape/distribution, but, again, this is just a proof of concept. More importantly, this brings my post count to 10, so I now have the permissions to edit my earlier post that got scrambled.