Why you have anything in emissive channel? You need to setup opacity channel if you use two-sided foliage model. For normals I suggest you to just make it point same direction as surface.(worldspace up.) Then it will look nice from all direction and it looks just like underlying landspace.
Yea I would do what Jenny Gore suggested, but control it with a Lerp, with a scalar parameter so that you can blend in a little bit of the actual blade normal. Also I would try playing with the opacity value as well as the basecolor and subsurface colors. Sometimes its necessary to make the basecolor a bit darker and the subsurface color a bit brighter.
Didn’t see this mentioned, but is this for static or dynamic lighting? Only dynamic lighting really works correctly with subsurface lighting models.