I’ve tried this in the official 2.78c release, using CPU render, when i direct the hair system to use a SSS material it will show up as BLACK rather than the correct SSS. I have tried it using the cycles BSSRDF shader, and have also tried it with the Principled BSDF in the latest Beta version of Blender, both had the same result. The material will render correctly on other objects but when applied to hair it shows up as black.
Probably, because hair uses its own space optimizations which is not completely compatible with SSS optimizations.
You can still use a mesh as your hair (i.e. using the particle instance modifier), and that way the material for the hair object can be SSS or any other shader.
Another possibility is to use the HairBsdf set to ‘Transmission’ (not really SSS, i know, but close).
Oh right… I was just trying to make a realistic grass material and figured it should have SSS…
Translucency should be enough. Maybe some rough refraction if you want back glow as well, in which case you need to handle the inverse normal (1/IOR for backface) and prevent infinite volume (incoming rather than normal).