Hello,

I'm work on bugfixes in Forestry and noticed that NSaplings will not grow on humus, which is the soil used for Forestry's multifarms. It all comes down to NSaplingBlock canThisPlantGrowOnThisBlock, which is quite strict.

   public boolean canThisPlantGrowOnThisBlock (Block id)
    {
        return id == Blocks.grass || id == Blocks.dirt || id == Blocks.soul_sand || id == Blocks.netherrack || id == NContent.taintedSoil;
    }

The OverworldSaplings grow just fine, so hopefully there is a simple solution.
I don't think we should be able to grow the bloodwood saplings on humus, but some of the others would be nice.

Steps to reproduce:

1. Put down a block of humus.
2. Try to place a Sakura Sapling on it.

Thank you! 🐝

Checked on Forestry 3.0.0.125 and natura-1.7.10-2.2.0-b1

I'm working on a PR involving saplings, just a heads up.