Using Grass Essentials, I'm able to add grass to my scene and distribute it according to my weight-painted terrain. Everything looks great and the scene renders properly -- until you save and reopen the Blend file. Upon opening, the particles are suspended above the plane and have lost all appearance of grass. Not sure why it displays fine while editing, but saving makes it go wonky. Any help is much appreciated!
Fixed. Apparently there was a group handling issue with Blender 2.78 which, in the case of Grass Essentials, caused the grass to basically disappear. I upgraded to 2.78c and the grass displays accurately upon re-opening the file.