1.19 Custom Biomes not spawning trees

I'm trying to make a custom biome but no trees are spawning in 1.19. I originally created it in 1.18 and it worked perfectly, but now that I'm updating to 1.19 and recreating my mod its not spawning any trees.

I've tried changing between vanilla and custom trees, and changing the ground between moss and grass and neither spawn trees. It's working with everything else (like particles etc) but generating it like an empty field.