herbo

One root covers grass and culinary or medicinal herbs, and context does the sorting, though kuracherbo spells out a medicinal one when you need to be clear. Grass as a lawn or expanse is usually herbo or herbejo, that last built with -ej- for the place, meaning a meadow. Note the number: singular herbo is the mass of it, plural herboj counts individual plants or kinds, which is why the last sentence above works. The adjective herba is unremarkable, and herbomanĝanto is a herbivore if you ever need it.