Demeter was the Greek goddess of agriculture. She was Zeus' sister and the mother of Persephone. Persephone was taken to the Underworld by Hades to be her queen. Demeter became distraught looking for her daughter, and the crops of the land began to die. An indefinite winter began. Hades was persuaded to return Persephone to Demeter for half the year. Whenever Persephone is with her mother it is spring and summer, whenever she is with Hades it becomes fall and winter.