Major changes:
Trees for Dark Forest. Dark Forest darkness varies, causing the spawning rate to vary from place to place. Put Better Trees into Windswept Forest and Windswept Savanna Attempts to move game start spawn in trees to ground.
Minor design changes Increased average size of Savanna trees. Leafier large birch More branches on medium spruce. Lowered chance of beehives Enabled Better Trees to generate below y=64 Adjustments to savanna trees Less variability in swamp tree density
Debugging
Fixed a deep bug in the tree branch code. Trees generate properly over water.
Internal changes Made variable tree reentrant for multiprocessing Better performance on initial world generation. Moved control of light level from trees to biomes.
Added shrubs. They are generally rare except in forests severely stunted by cold and/or altitude.
Better Forests now affects swamps; they vary in height and density, and sometimes have dead trees, occasionally only dead trees.
Added Swamp Willow
Fewer Beehives on evergreens
Fixed a bug blocking sapling generation
Reduced stunting with altitude for Grove and Acacia trees.
Fixed a bug with biome-specific height changes
Fixed a memory leak and improved performance
0.3 Changes
Marked for 1.20.1 to 1.20.6, but only tested on 1.20.1
Altered tree type variability to use current climate system. Generic oak biomes like Plains and Forests now change from mixed spuce and oak in cold regions to pure oak in cool regions to mixed birch and oak in warm regions. Other forests mix in trees from climactically close biomes.
Added Better Forest trees and techniques to Plains, Flower Forest, Snowy Plains, Snowy Taiga, and Grove.
Some speed improvements.
Reduced density of new Savanna trees.
More naturalistic Acacia trees.
Groups of saplings can grow into the RTG trees. Larger groups, up to 3x3, grow into larger trees. Lone saplings and (when appropriate) 2x2 groups grow vanilla trees.
Trees with mixed blocks can be grown from mixed saplings. The sapling in the center determines the form of the tree; the most common sapling around it the logs; and the second most common sapling around it the leaves (or the most common if there is only one). This can grow Dark Oak and Jungle materials even though Better Forests currently doesn't have trees for them; an Oak sapling with Dark Oak saplings around it will be an oak-shaped tree made of Dark Oak wood and leaves. So, yes, you can farm Dark Oak.
Bugfix: Fewer missing trunk blocks.
Initial Beta