How can I avoid a gap in my foliage due to slope

How can I avoid this problem of gap in the foliage when the slope increases ? I’ve made a procedural foliage using the grass output in my landscape material but I’ve always problems dealing with distance and slope.

I’ve already tried without success :

  • changing my foliage to follow the normal of the terrain,
  • modifications on the screensize threshold between LOD level in my foliage
  • modify the density of my foliage but it’s already really dense

What are you basing the Grass node on? Normally it’s either the angle of the terrain, or it just samples one of the landscape textures.