The poem starts with the dry language of a plant guide. Cutleaf toothwort has leaves "deeply divided & coarsely toothed," and the speaker plays with that wording, imagining it describes a barbarian horde. The joke keeps going: even the roots have tooth-like bumps, and they're said to taste peppery, whether eaten raw, boiled, pickled, or fermented until sweet. The speaker sums it up with a pun, calling the plant "a toothsome thing."
Then the poem turns. A mordellid beetle, sitting on a petal, knows none of these human descriptions. It is simply drawn in by the flower's scent, which the speaker says is nothing like a "fetid snaggle of teeth."
The tone is light, amused, and a little teasing. The speaker seems to enjoy how much language we pile onto a plant, yet the ending suggests that the beetle's plain, direct experience of the flower matters more than our labels.