Lines 1–4
The speaker begins by noting the season and the general weather. It is May, when flowers are just beginning to bloom; an off-shore breeze has inspired him (and, noting the plural use of "solitudes," possibly a companion) to take a walk. He then describes coming upon the rhodora and its immediate surroundings, which seem to indicate that the plant is alone in an otherwise none too thrilling spot: it is a damp nook or corner; the brook is not babbling happily, but sluggishly. He even uses the word "desert," which seems oddly misplaced for this part of the world, especially given the description of the nook. However, the New England spring comes notoriously late, following several months of very muddy conditions, so perhaps it is the desert of mud—with no other blooms in sight—that Emerson is referring to. As line 3 reveals, the rhodora is a shrub that blooms before its leaves appear, meaning that the petals stand out in stark relief.
Lines 5–6
With the alliterative "P's" in line 5, Emerson uses the most musical line in the poem to describe the flower itself. Notice, though, that the petals have fallen into a pool of black water, which might mean that it is really more of a stagnant puddle, an image that is consistent with the sluggish brook of line 4. Perhaps the speaker was particularly struck by the purple blooms because they were in such an otherwise unattractive water, just as the water brought a special beauty to the otherwise simple petals.
Lines 7–8
Emerson continues to add colors, as "red-bird" joins the purple petals and black water. The bird's plumes will be outdone, says the speaker, by the flower's color. He also uses the word "court," which hints at the fertility of spring.
Lines 9–10
As the second half of the poem starts, the speaker shifts and addresses the flower, rather than the companion whose question inspired the poem. He even uses an exclamation point to add a celebratory verve to the line. The rest of this couplet, and the two lines that follow, have an implication of Emerson's impatience with those who would elevate Man above Nature. Readers might even hear a certain sarcasm for the so-called sages who fail to appreciate the flower's charm or beauty, as well as the majesty of the earth and sky.
Lines 11–12
The use of the affectionate term "dear" personalizes the flower even more. The speaker also cleverly plays off those who would ask, and have asked, "what's the purpose of this flower?" by pointedly remarking that the purpose of one's eyes is to appreciate beauty for its own sake, without asking the flower to justify its existence.