The "cactus land" and the "dead land" are different representations of the kingdom of death within the poem. The structure of the text is a series of contrasting images of sterility and fertility. For example, rather than "Here we go round the mulberry bush," a traditional symbol of fertility, we have "Here we go round the prickly pear," bringing back the cactus imagery, and conjuring images of a dry, deserted land, where only harsh cacti grow.
These lands are reflective of Eliot's vision of his society. As a writer in the modernist movement, Eliot's works reflect an American society that is spiritually empty, a world where spirituality is passed over in favor of greed and consumption. Thus, the cactus land and the dead land are the American culture at the time through Eliot's eyes-devoid of life, soil on which nothing can grow.
This poem also follows the tradition of the Fisher King myth. The most popular incarnation of this myth is the King Arthur legend, but more generally, it involves a ruler who has suffered an injury which has weakened his physical state. This injury is also reflected in his spiritual state, and in his land, which slowly dies as a result of his fragmentation. In the myth, a young, whole knight (Lancelot, for example) redeems the kingdom with his virility and purity. In this poem, we have the wasteland, empty and dead, with no hope of redemption.