How does the harvest of grapes relate to the Greek gods Dionysus and Demeter?
The connection between Dionysus and the grape harvest is explicit. He was in fact worshipped as the god of the grape harvest and of both the production and the consumption of wine. Because of the effects of alcohol, he was also associated with festiveness, madness, and ecstacy. But his main association was with wine, and wine makers would pray and offer sacrifices to him in order to ensure a good crop. He was, however, one of the last of the classical Greek gods to enter into the pantheon of common worship. In the words of Greek mythology expert Edith Hamilton:
Everywhere he [Dionysus] taught men the culture of the vine and the mysteries of his worship and everywhere they accepted him as a god until he drew near to his home country.
Demeter, on the other hand, was associated with crop fertility and the harvest in general, though usually with grain harvests (Dionysus was worshipped in this capacity in some regions of the Mediterranean, as well). She was not directly associated with wine, though as a goddess of agriculture fertility, who also controlled the seasons, was probably invoked by grape as well as cereal producers.