Spring comes in as an infestation. Tent caterpillars appear "just as the leaves burst their buds," and the speaker, whose father is about to have a large tumour removed from his lower spine, cannot help seeing the two things as one. The central idea is that a medical event can be understood as an exorcism, and that the natural world quietly carries out the same ritual that the surgeon performs. The title, "Incantation," announces the method: surgery is imagined as a spell, and the poem ends by letting a bird speak it.
The first image is a small, almost playful one. The white tents look "as if someone with a white marker / were doodling in every crotch of limbs." It is a casual, slightly irreverent simile, the way a person talks when they are not yet worried. Then the tone shifts. The tumour becomes "a white knot swelling / with caterpillars of pain," and the doodle turns into something inside a body. The silk nests in the trees have become a picture of what is wrong with the father, and the metaphor does the frightening work without any need for dramatic adjectives.
The language of the middle section moves between the clinical and the magical. "Non-malignant" and "lower spine" belong to a hospital report, but "cast out" belongs to folk belief, and "the surgeon's art" cleverly sits between the two, since "art" can mean skill or enchantment. The tumour is "excised, exposed," two words whose matching *ex-* sounds make the removal feel quick and clean. Then comes the poem's best phrase: "bulb that burned / but gave off no light." Here the tumour is a light bulb that produced only heat, and also a plant bulb that produced only a "sexless flower," a bloom that can never set seed. Calling it an "empty tent" works the same way, because tent caterpillars leave their tents behind when they move on. The pain has gone, and what remains is a husk.
There is no rhyme, and the lines are loose and uneven, but the poem controls its pace carefully. The long, winding sentences about the father's weeks of pain, when he was "forcing him to stand or to walk / slowly for hours each day," mimic the slow pacing they describe. Enjambment also lets the poem take a step at the right moment: "he's taking / his first steps without it." Against all this, the closing fragments of the first stanza hit hard: "Sexless flower. Empty tent. / Be gone. Be gone. Be gone." The triple repetition is the spell itself, and its bluntness shows how badly the speaker wanted the thing gone. The ampersands scattered through the poem keep the voice informal and notebook-like, so that the incantation arrives as a private outburst rather than a performance.
The second stanza moves outdoors, to the woods where the father will resume walking, "this time to heal rather than assuage." That small contrast carries a lot, because the same walking that once only dulled the pain now has a different purpose. A tanager appears in "flashes of scarlet," and the colour is a sharp jolt after all the white. The bird snatches "gnats & caterpillars" from "the not quite fully opened leaves." That last phrase is worth noticing, since it suggests recovery as something still unfolding rather than finished.
The ending is where the poem's idea becomes physical. The tanager sings "a line of his hoarse song / between each mouthful of wings, / each mouthful of spines." The bird is literally eating the caterpillars, so the "caterpillars of pain" from the earlier metaphor are being swallowed, spines and all. The song set between the mouthfuls reads like a repeated chant, and the word "his" sits close enough to the father that the bird seems to share his voice for a moment. That link is only suggested, but it is the right kind of suggestion for a poem this restrained.
What makes the poem worth reading is its refusal to be sentimental. It is relieved, but it shows the relief through images rather than announcing it. The medical facts stay plain, the magic stays small and homemade, and nature is no vague comfort but something that does a job. By the last line the spell has been completed by a bird, which is an odd and satisfying way for a poem about fear to end.