Already her dark pod is cooking its drug. Every breath imperils her. Her crucible Is falling apart with its own fierceness.
OK, so, blatant drug talk this time – none of this "Mafia Queen" subtle stuff. Now we have a direct reference to the fact that when this poppy reaches maturity, it will contain opium in its seed pod.
Why the "already," though? This is probably a reference to how short-lived the flowering actually is. Think, if you know of them, of magnolia trees. Or cherry blossoms (like the ones in Washington, DC). They positively explode with color, but then they're gone within a week. So even though the poppy might have just burst into bloom, it's going to be short lived.
The next line corroborates (which is just a fancy way of saying "supports") our particular hypothesis here, as it notes that "every breath imperils her." When your life is only a week long or so, each moment – personified here as a "breath" – counts and could be your last.
Vocab time! What's a "crucible?" (Besides a dark play about witch trials by Arthur Miller, that is.) Well, in industry, a crucible is a cup-shaped tool used to heat stuff – everything from chemicals to steel. The important part is that a crucible is used with extremely high temperatures. Otherwise, it's just a cup.
So why call the cup of the poppy a "crucible"? Maybe there's something too hot to handle here…
(We are so clever! So is Ted Hughes!)
Problem, however – the crucible is "falling apart." Yikes. If a crucible is supposed to be able to handle extraordinarily hot things, and this poppy is still too fierce to even be called a crucible, it must really be something incredible. Maybe like a firework, temporary and huge and really very bright, but also exploding, and therefore unable to be contained.