Nature, Nature, and Nature
Roethke was a nature lover and his poems are filled with the stuff. There are the things you'd expect: birds, trees, flowers and the like. But his poems also employ the less poeticized, less sentimental aspects of nature like mold, mildew, and weeds. For Roethke, looking at nature was a way to understand and explain life—from our physical existence to deeper, more psychological aspects.
If you dig Roethke's nature heavy poems, check out "The Minimal," "'Long Live the Weeds,'" and "A Light Breather" to get more dirt under your nails.