Bleeding inwardly Her maternal nectars into her own Coffin – (cradle of her offspring).
And we were right – this flower is not going out quietly!
So we have internal bleeding, right off the bat. After the poppy's petals fall off, it begins to form a large seed pod. To do this, it has to invest pretty much all of its energy into growing that pod. That might be a kind of "bleeding," no? Like something that "bleeds you dry"?
The next line helps us along some, by telling us that what's "bleeding" is the poppy's "maternal nectars," but that latter phrase is kind of odd. What's "maternal nectar"? We think that it probably refers to all the plant's energy – literal nectar, but also all the sugars and products of photosynthesis that are coursing through a plant at any given time – that go into producing seeds. Hence the "maternal" part. The poppy is now a mom.
The problem with being a flower mom in this case, however, is that it literally does bleed the poppy dry. The formation of the seeds is the last thing the flower will do before it dies, and the poem takes note of this in a rather chilling way by calling the pod a "coffin."
And if that weren't creepy enough, the poem's next word after coffin is "cradle"! Although to be fair, it also has a kind of nice, circle-of-life ring to it. (And that's the last Lion King reference we'll make in this analysis, we promise.)