The speaker addresses goatweed, a plant, as if it were a lover, and then blurs the line between the plant and his own body. Yellow flowers seem to bloom between his shoulder blades, in a place where the sun "too weak to rise" never reaches. That image suggests something growing inside him, perhaps illness, age, or medication, though the poem never says so outright. The mention of not being able to "get it up" and of playing "badly with other medicines" hints at a body in decline.
Yet the feeling is oddly joyful. Calling himself a "shaman fundamentalist" is half joking, half serious, and he admits his "dry bones" feel more alive than ever. The mood is tender, funny, and a little dizzy, mixing anxiety with gratitude. The last line, where he grows a "green husk" in the otherworld, turns decay into renewal: he becomes a kind of plant himself, and that seems to comfort him.