No matter what or whom you believe in, in the end, you are still faced with your own mortality. This moment in the poem is the first time that mortals are addressed. After all, gods aren't supposed to die, right? It's a hint that Dove might be talking more about us humans than she is about her Greek myth.
what ground opened to waste (8)
Dove's language in this line makes it seem like the ground chose to produce no flowers, only waste. But we know that Demeter caused the famine, and later winter, that made growing anything difficult.
though you dreamed a wealth of flowers. (9-10)
Dove uses particular language ("wealth") to indicate that flowers are something valuable. In this poem, Demeter uses agriculture as a symbol for the results of Hades' actions, and our own. If Hades dreamed that the results of his marriage to Persephone would bring a "wealth of flowers" but instead it brought only waste, he must have been quite disappointed.