Currently red roses are generated instead of vampire orchids are generated in the vampire forest, since the forge mechanism does not does what it seems.
Either wait until Forge is fixed or implement a workaround.
Flower Generation: BiomeDecorator around line 200

me too

Solved by replacing the yellowFlowerGenerator in the biomes BiomeDecorator (on every call of decorate, don't now why setting it in the constructor is not enought)