There is a problem with all the AbyssalCraft grasses and dirts, other than vanilla flowers and bushese, no ones of other mods bushes and flowers can be placed on them. You maybe forget to register them as dirt and grass blocks.

That's not how that works, but since it's a pretty small thing to do, I might as well apply the necessary changes on my end. If this still doesn't work in the next version, that'll be on the other dev's end.

Now all trees can grow on dark and dread grass, while I suppose they shouldn't...