"Butterfly weed"—it only sounds half special, when you think about it. Who doesn't love butterflies, but then who doesn't hate weeds? It sounds like a complicated plant if you ask us, but in the poem this flower is not so difficult to understand. At first, the speaker is standing out alone in the field, convinced that he's utterly on his own. And then—boom—he notices that tuft of flowers and his whole worldview changes. In this way, the flowers are at once a symbol of the mower's presence and a reminder to the speaker that he's connected to others.
Lines 14-16: The first flower we hear about is the one from "of yesterday's delight" (14). This was a prime chill spot for the butterfly, but now it's been cut down and the butterfly is left without a place to rest his wings. Observing this, the speaker's sense of isolation seems to intensify.
Lines 22-24: The tuft of flowers that's been spared by the mower really jerks the speaker out of his doldrums. This discovery sets him on a whole new footing, emotionally speaking.
Line 23: The metaphor of the flowers as a "leaping tongue" seems to suggest that the speaker, who's been asking questions with no reply (back in line 19), might finally encounter some communication about his problems.
Lines 27-28: Sure enough, the speaker sees the flowers as a sign of the mower's love. Whoever was cutting the field saw them, appreciated their beauty, and left them there. Still, it doesn't look like the mower was handing out any personal favors when he (or she) did this.
Lines 29-30: At the same time, the mower wasn't trying to draw any attention by saving the flowers. The speaker instead sees this as a pure expression of the mower's happiness to see the flowers. Isn't that sweet?
Lines 32: These flowers are more than just flowers now. They're a message, letting the speaker know that he's not really alone, even if he's by himself in the middle of field. There are traces of other folks all around him, like these flowers.