Critics consider "Mushrooms" to be about feminism. The mushrooms are symbols for women who are growing into their rightful place in society.
Sylvia Plath frequently wrote about feminist themes. As a female poet in 1950s America, she often felt torn between being a good wife and mother and being a professional writer. The poem "Mushrooms" uses metaphor to describe the plight of American women in that decade.
Plath speaks in the voice of one of the mushrooms throughout the poem. She refers to the mushrooms as "us" and "we." She describes the mushrooms as "Perfectly voiceless," as many women in that era felt themselves to be. The mushrooms grow "discretely, / Very quietly." The mushrooms are acting as women were expected to act: demure and quiet. The mushrooms are unassuming and undemanding, "Bland-mannered, asking / Little or nothing."
However, the poem subtly implies an approaching uprising. The language hints at qualities of inner strength in the mushrooms, their "Soft fists insist on / Heaving the needles." They are so determined to grow that they even lift obstacles as heavy as "the paving," or the sidewalk.
"We shall by morning / Inherit the earth," Plath writes in the last stanza. This is a reference to the Biblical passage, "The meek shall inherit the earth." In other words, although the mushrooms (and 1950s American women) are unappreciated today, tomorrow they will rise to a position of power.