Robert Frost's theme in the poem "birches" is one of, Life (on earth) is probably the best place to engage in sex and do not wait until you go to heaven. Imagery, diction, and sound/musical are all essential elements in conveying the poems meaning. Throughout the poem, images of sexual contact, words relating to sex, and an alliteration that describes the act itself, are presented to help reveal to true meaning of the poem. .
Throughout the poem, Frost creates images that are hidden. These images presented help provide evidence of sexual feeling. The image of "trunks arching in the woods" and "Like girls on hands and knee" creates the sexual emotion. Not many girls go into the forest to dry their hair and the "trunks arching in the woods" can either mean trunks of trees or the trunk of a man. The image of the boy "riding them over and over again" can relate to the act of sex. And how the boy "launched out too soon" or early ejaculation. Frost also refers that all these acts of passion should be here on earth, "Earth's the right place for love." All these images can relate to sexual feelings and all help to get a better understanding of the poems true meaning.
Frost's undecisive diction can relate also to sex. The connotation of the words that the author uses helps portray an act of passion of sexual feeling. How the boy "cracks and crazes" the enamel can also relate to the act of intercourse. The definition of crack is an opening (woman's organ) and the definition of craze is a temporary enthusiasm (intercourse). Also how the boy "swings" from branch to branch, or rather moves to woman to woman. "Snatch", "dome", "crust", "ice storm" and "limp" all in a way, maybe slang, relate to sexual feelings and these words help convey the meaning of sex.
The Poem also consists of alliteration and has bits and pieces of an iambic feet. The only part where alliteration is present is when Frost is describing the act of sex, "soon the sun's warmth makes them shed crystal shells, shattering and avalanching on the show-crust- Once again, it is the words in the quote that can relate to the feelings of sex, "shattering", "crust", "sun's warmth", and "shed.