Dave Bonta starts with the word itself: "thorn" was also a letter in the Old English alphabet, now obsolete. From there the poem turns to the plant part, which it describes in sharp, surprising images: a branch that never finished growing, a "weaponized nipple" that draws blood where you'd expect sap or milk. The nod to nature "red in tooth & claw" reminds us that the natural world isn't gentle.
The tone is playful and a little wry. The speaker seems to enjoy how language and nature overlap, piling up comparisons the way a thorn piles up scratches. Then the ending shifts. Bees aren't bothered by thorns at all, and the closing question, "who needs a needle / to thread the seamless labyrinth / of the rose?", suggests that what looks like a threat to us is irrelevant to them. The mood moves from prickly and defensive to quietly delighted, with the rose's beauty winning out.