plants

Plants
-Block Methods
--getPlantTypes() @Nullable Set<PlantType>, null type represents not a plant.
--canBePlanted(IBlockReader, BlockPos) boolean, Plant's authority on if it can be placed here. Equal authority with canPlantOn
--canHarvest(IBlockReader, BlockPos,  @Nullable PlayerEntity) boolean, if the plant can be harvested
--harvest(IWorld, BlockPos,  @Nullable PlayerEntity) List<ItemStack>, harvests the plant into a List<ItemStacK>.  Updates the state in the world.
--placePlant(IWorld, BlockPos, @Nullable PlayerEntity, ItemStack) boolean, places the plant into the world.  Returns true for success.
--getSeed() Item, returns the seed for this plant.
--getGrowthProgress(BlockState) float, returns [0, 1] for plant growth.

-Growing
--Handled by IGrowable. 
--IGrowable needs an ItemStack context for what the fertilizer is.

Soils
-Block Methods
--canPlantHere(Block plant, IBlockReader world, BlockPos pos) boolean, Soil's authority on if a plant can be planted here.  Equal authority with canBePlanted
--getSupportedPlantTypes() Set<PlantType>, less contextul method that gets what types this plant should supports.

Seeds
-Item Methods
--canBePlanted(IBlockReader, BlockPos), delegates to Block
--placePlant(IWorld, BlockPos, @Nullable PlayerEntity, ItemStack), delegates to Block
--getPlantState(IBlockReader, BlockPos, @Nullable PlayerEntity, ItemStack) BlockState, gets the state this plant will place.  Not always accurate due to doubleplants etc.
--getPlant() Block, returns the Plant associated with this Seed

--getPlantTypes() @Nullable Set<PlantType>, null type represents not a plant.
It would be better if things that aren't plants just return an empty set.