dynamic grass

After doing a bit more research, I realized that it may be possible to use particles to render grass fields.. I think I may look into this more.

You might be able to get some ideas from here.

I haven't tested this, but I think it might work:

If you've got connectivity information for your mesh (i.e. you know which other faces each face is touching), then it should be trivial to determine which edges you're seeing 'edge on' (i.e. one face is facing you, the other is facing away). Then, for each edge that is 'edge on', place a quad with a side-view grass texture with its bottom on the edge and the top however far up you want the grass to be.

You could do it for all edges, but the above technique should draw notably less geometry. With a suitable top-down grass texture for the terrain itself, it might be convincing.