This is basically what I mean. I tried to imitate the LOD effect in unity using crossfade LOD but it's not nearly as seamless. I've done some research into the subject but can't seem to find anything about blending foliage in this way so I'm looking for advice. Thanks so much!
One often-overlooked visual aspect of stuff like grass or hair (ie. tufts of stuff sprouting out of a surface) is how the normals affect lighting. Specifically, because the default normals stick straight out of the blades of grass, the grass has normals perpendicular to the ground and are lit very differently from the ground. Instead, point the grass normals straight up along with the ground so the grass is lit the same as the ground.
I discussed this same issue on my blog recently in the context of hair on a character I modeled. Meanwhile, this polycount article discusses the same issue/trick for foliage. In particular, check out these screenshots to see how the grass looks before and after aligning normals with the ground.
The actual mechanics of tweaking normals depends on your art tool. For example, here's an explanation of how to do it in Blender. Obviously generating appropriate normals is very straightforward if your grass geometry is created procedurally.