[1.15] How to Control What Blocks a Tree Can Spawn On

[Hoping1]

I'm trying to make a biome where the top layer is snow blocks, but of course, no trees are spawning. My immediate solution is just to copy one of the existing tree classes and modify it so it can spawn on snow blocks. How do I do that? Where are the blocks it can spawn on set?

[Hoping1]

Anyone?

[LTNightshade]

Looking at SaplingBlock from Minecraft, it extends BushBlock what has a function:
 

protected boolean isValidGround(BlockState state, IBlockReader worldIn, BlockPos pos) {
      Block block = state.getBlock();
      return block == Blocks.GRASS_BLOCK || block == Blocks.DIRT || block == Blocks.COARSE_DIRT || block == Blocks.PODZOL || block == Blocks.FARMLAND;
   }

 

would suggest, override this method...

 

[Hoping1]

Worked like a charm, thanks! Fancy trees are a little more complicated but I worked them out the same way and looking at the defaultbiomefeatures.java if anyone's curious.