There are currently restrictions on certain sacrifices like animated trees and breeders/summons to prevent or restrict the numbers of easy sources of piety. The same should apply to stomafilla, which can be easily farmed to give large amounts of piety, even giving several easy precrowns early in the game. A god should only accept around 10 before saying "ENOUGH WITH THE HERBS, ALREADY. I WANT SOMETHING MORE MEATY!"

An alternative would be to reduce the piety gained from stomafilla to around a tenth its current value. This would still allow scumming/farming, but would make it so tedious that it would be beyond the effort of most sane players.