Mrs. Brown is a woman who lives in the area of Oklahoma where the story takes place; her home is within walking distance from Bilie Jo's house. Mrs. Brown owns a cereus plant, a desert cactus variety which blooms in the night. Mrs. Brown has sent word that the plant will be blooming on Saturday night, and has promised that Billie Jo can come and see it. Had her mother been alive, she would not have allowed Billie Jo to go alone so late at night, but in her mother's absence, Billie Jo's father just stands in the doorway and watches Billy Jo leave.
A small crowd has gathered at Mrs. Brown's when Billie Jo arrives at three in the morning. The blossom had opened at midnight, "when the sun couldn't scorch it, when the wind was quiet." Billie Jo wonders how "such a flower (can) find a way to bloom in this drought," but bloom it does. At dawn, in the first morning light, the flower will wilt and die, but Billie Jo does not stay to see this.
The cereus flower is symbolic of Billie Jo's life, and her potential to bloom even in the stark, unforgiving environment of the Oklahoma dustbowl. The fact that Billie Jo does not stay to see its demise when the sun rises might be indicative that she herself will not wither away when harder times come, but will have moved on to live a full life, in celebration of her own awakening ("Night Bloomer - September 1934").