I found a solution for missing grass that worked for me. Just to mention, I'm playing Skyrim LE on Linux, and am using Vortex. Anyway, I found Vortex's and Skyrim's launcher's load order don't match. Skyrim's launcher made an order of its own, ignoring Vortex, and it was the culprit for the missing grass. It was putting the mods' .esps higher up on the list instead of lower, thus letting something else to override the grass mods. It was doing the same thing with my SkyUI. So, I put my grass mods after everything else in Skyrim's launcher under DATA tab, and voila, I got all the grass. I'm using Unique Grasses and Groundcovers, combined with Flower Fields. Hope this helps. Cheers