In my opinion, the main message of "The Winnebago Trickster Cycle" is that humans should be wary of considering themselves above the natural world. These are all simple stories to teach valuable lessons. It has value for young and old, alike.
Of course, Trickster is the "cultural hero" of all of the stories who always lives up to his name. The myths chronicle his adventures while spirits enter the world to save humanity from their enemies. Humans are not indestructible, and nature has a way of always reminding people of this: natural disasters, herbal poisons, biting insects, you name it. Trickster often doesn't heed the messages of nature and learns from it (such as in the case of eating the bulb that promises defecation). In another situation Trickster thinks that people aren't paying attention to him, so he engages them in competition. Ironically, the "people" aren't really people at all, but are plants and other forms of vegetation. Trickster, therefore, acquires more wisdom through trial and error.
The world is going to be a difficult place to live in and I am trying to find some clean place in which to dwell.
Thus remains the perfect mini-explanation of Trickster's journeys.