Sublime
Plath’s description of the blackberries and of the sea evokes a simultaneous sense of awe and reverence best characterized in the idea of the “sublime.” The idea of the sublime was hotly debated in the eighteenth century and later appeared in the work of romantic poets such as William Wordsworth, whose writing is marked by speakers aware of their own smallness in relation to the grandeur and might of nature. The final image of “Blackberrying” adds terror to the sense of awe, as the speaker describes

a great space
Of white and pewter lights, and a din like silversmiths
Beating and beating at an intractable metal.

Consciousness
In packing her poem with images of life’s abundance and death’s inevitability, Plath points to the uniqueness and the “problem” of human existence: human beings are aware that they will die and there is nothing they can do to change that. Her numerous metaphors and similes for the fruit underscore her joy at life’s abundance, and her personification of the berries shows her emotional attachment to the natural world. This personification occurs in the last two lines of the first stanza when, after the speaker’s fingers are covered with juice, she says, “I had not asked for such a blood sisterhood; they must love me; / They accommodate themselves to my milkbottle, flattening their sides.” Her sense of death is embodied in the images of the “the choughs in black, cacophonous flocks,” and “the hills’ northern face . . . / That looks out on nothing.”

Nature
Nature isn’t always a pretty place where flowers bloom and cute animals frolic in the sun. It is governed by the cycle of life and death, and the fact that a part of nature must die for another part to live. “Blackberrying” de-romanticizes nature in the image of the “bush of berries so ripe it is a bush of flies, / Hanging their bluegreen bellies and their wing panes in a Chinese screen. “ This image of nature cannibalizing itself brings to mind German philosopher, Freidrich Nietzsche’s words, “All that is ripe wants to die.”

Journey
The speaker’s journey through the lane of berries is analogous to the human journey through life. Sometimes people feel hemmed in on all sides by life’s pressures, just as Plath’s speaker feels surrounded by berries. The “hooks” in the poem, on one level part of the literal shape of the alley, can be read as events that change the direction of one’s journey through life. Throughout the speaker’s walk through the alley of berries, she encounters signs—flies feeding on a bush berries, the “cacophonous flocks” of crows—full of meaning that only she can understand but not necessarily communicate to others. This is similar to how many people experience incidents and events in their own lives, seeing signs in nature that are ominous yet impossible to decode.