Describe symbolism in Buried Child by Sam Shepard

Some of the strongest symbols in Buried Child are related to nature and fertility and reinforce the play's central image: the dead, buried child in the field. The vegetables Tilden continuously carries into the house are one such symbol. Crops have not been raised on the family farm for many years. In all that time, the fields have gone unplanted and have grown over with weeds and scrub brush. Still, Tilden manages to harvest the fallow fields, just as he was capable of conceiving a child with his own middle-aged mother years before (it is suggested that Halie was past menopause, and therefore fallow herself, when her tryst with Tilden occurred). Realistically, his harvest is nonsensical, but as a symbol, it complements his dreadful act of incest and illustrates his obsession with his lost child, his need to pull life from the dead ground.