"The Rhodora" is filled with personification as the speaker repeatedly grants human characteristics to various aspects of nature. All this personification supports one of the poem's central arguments: that human beings and nature are kindred spirits because they are both God's creations.
The speaker personifies nature for the first time in line 4, describing the rhodora as "pleasing" the landscape and the nearby "sluggish" brook. The rhodora's petals also make "the black water" of a puddle (or perhaps that same brook) "gay," or happy. By attributing human emotions to their natural surroundings, the speaker illustrates the healing power of the rhodora's beauty.
Of course, this also might be read as an example of pathetic fallacy—as the speaker projecting their own emotions onto the landscape. Still, the language brings the environment to life, emphasizing that people may find a sense of fulfillment and connection by engaging with the natural world.
The speaker also personifies a bird to show that even some of nature’s most beautiful creations cannot compare to the rhodora. The "red-bird" in line 8 attempts to "court," or woo, the rhodora, but the flower petals outshine the bird's own "array" of red feathers.
Finally, the speaker treats the rhodora itself as remarkably human-like throughout the poem. The speaker addresses the flower directly several times through apostrophe and instructs the rhodora to defend itself against sages who question the larger purpose of its beauty. The speaker treats the rhodora like a being with will and agency because, on a certain level, the speaker views them as equals. Both come from God, and the speaker thus feels intimately connected to the flower.