[1.12] Make a biome with no flowers/grass

[JimiIT92 19]

I want to make a biome without flowers or tall grass. So i've done this in my biome's constructor

this.flowers.clear();
this.decorator.grassPerChunk = 0;
this.decorator.flowersPerChunk = 0;

 

But both flowers and tall grass still spawns. So how can i totally get rid of this?