Roethke uses nature imagery to convey the grief and sense of loss in "Elegy for Jane." But he also uses nature imagery to show Jane's happiness. Roethke found answers and solace in the natural world. For him, nearly every aspect of life could be explained and demonstrated by carefully considering the natural world and our relationship with it.
Roethke believes that the only way to truly understand the human mind and human nature is to understand nature itself. Deep, dude.
Roethke needs to give it a rest with the twigs, branches, and mold. There is more to the world than nature.