The speaker imagines a future home with a garden, and the first nine lines are calm and practical. They list what they'll plant: mustard greens, tomatoes, radishes, turnips, plus mesquite stakes for the vines and a touch of pine. They picture the end of a day's work, wiping resin from their hands and rinsing off sweat and dust in a washbasin.
Then the poem turns. The repeated "down, down, down, down" and "drain, drain, drain" make the water feel like it is sinking into the ground, carrying the speaker's labor out into the fields. The last line, "There therein was Abel killed," brings in the biblical story of Cain murdering his brother Abel, a farmer's story about violence in the soil. Suddenly the garden isn't innocent. The speaker's sweat feeds land with a dark history, and the poem suggests that even honest work happens on ground that remembers a crime. The mood shifts from hopeful and domestic to uneasy and heavy, ending abruptly on that image.