Maybe? [ ah, Emporio seems... confused? surely more information might help? ] Some grass types can take in nutrients from the soil via their roots. Some of them can photosynthesize. But if they have a mouth they typically can and will eat food like the rest of us. ... Mostly. Can vary a lot between species.

[ that is, after all, kind of a recurring thing with pokemon. pokemon are many and varied.

beat. ]

A grass-type specialist would know more on the specifics.