A nice and decorative small fir tree with very dense twigs/branches in 6 sizes.

This design is inspired by tc_fea's Pine Tree and More Pine Trees from 2011, which seem to be the first ones of this kind, BQEducacion's Christmas Tree (2015) with decorations, ROBK636's Christmas Tree (2015), which introduced staggered branches, and abekabakoff's Christmas Tree (2021), which introduced randomness in branch orientations and lengths and also much denser branches, published as OpenSCAD script with many customizable parameters.

I wrote my OpenSCAD code for this tree from scratch, implementing doubled branch density (branches on every layer) and a recursive method to have random branch orientations while avoiding close orientations in adjacent layers. I also added a broader foot for more stable standing and a nicer tip (that's a matter of taste though).

Printing: vase mode, 0.2mm layer height
I also recommend OrcaSlicer, because it's “old” non-smooth vase mode option is better suited for this model. I wish PrusaSlicer let us choose between old and smooth vase mode, too.

Looks great in Prusament Galaxy Green.

Printing speed and cooling have influence on the lowest branches: The higher the speed and the lower the cooling, the more the lower branches will hang down (see image). Higher branches are not affected though due to the high density supporting them. You can also try to start slow and increase the speed mid-print.