You will have to download a 2.92 or 2.93 Build of Blender, which features geometrynodes and is experimental, for this Blend-File to work!

Each Tree consist of a trunk and a branch object, as well as at least one empty to control the overall look of the tree. 

Clicking Trunk or Branch object reveals several modifiers that object is build out of, you can change them.

One of the modifiers is the geometrynode modifier - click on the modifier to make it active and open a geometrynode-nodetree to see its contents (i.e. nodes it is made out of). All the essential values can be put in from outside the nodetree in the modifer itself.

rotation - a vector X, Y, Z that randomizes the rotation of the leafs or branches

density - amount of branches or leafs or lianas

scale min max - control the leaf size

Animationnodes L-System Setup

Min/Max Branches - Animationnodes creates a lot of Branches in the Background, with min max you specify how many of them will be visible - more will be harder to calculate

Thickness - Stem thickness

twisting - Stem and branches are build from curves - twisting makes them twist more or less

grow - it grows the tree from 0 to 1

Animation Duration - when Animate is enabled this specifys the Duration of the Animation

lower limit points - adjust how far down the twigs grow

Seed - Seed - change this to get a different looking tree

Min Max branch Rot - adjust how far the branches rotate - 0/0 will be a straight line upward

Min Max Step Size - Adjust ho tall your tree is and how long the branches are