How does Hades trick Persephone?

Persephone didn't eat anything down in the Underworld and until he gave her a promangate fruit.Zeus demaded that Hades give Persephone back to her Mother(Demeter) so she would let life back into the earth again.Hades said he will agree but how many seeds Peresphone eats then that's how many months she stays in the Underworld a year..Peresphone eats 6 seeds=spring,summer(she w her mother)and fall,winter=she down in the Underworld w Hades and her mother is mourning her.