In some ways, "The Wild Iris" is a painful poem. Suffering is front-and-center from the get-go, even though the speaker keeps predicting an end to it. It reminds us of those nurses who always assure you, "This will only hurt for a minute." (Does anybody really believe that?) Still, as we work our way through the poem, the theme of suffering expands in surprising directions, shedding unexpected light on the physical, emotional, and spiritual challenges of being human.
Fear is the root cause of much suffering. In the poem, the speaker argues that the fear associated with helplessness (being unable to speak) is a special kind of torture.
Creativity is not possible without suffering (hence the expression "suffering artist"). In the poem, the speaker must suffer in order to find a new voice, which symbolizes creativity.