Worship of Demeter as their goddess of all grains seems to have occurred primarily in connection to natural fertility. Every year during autumn, the festival of Thesmosphoria was held to honor the goddess.

On the very first day of the festival, Married women build leafy shelters and furnish them with couches which were made with plants. On the Second day, they had a fast. On the third day, a feast was held and they offer gifts of seed corn, cakes, fruits, and pigs to the goddess Demeter. They had a hope that Demeter who was their god would grant them a good harvest.