Analysis: What's Up With the Title?
The title of this poem announces its central metaphor. The poem is called "A Poison Tree," and at the end a "foe" lies "outstretched beneath a tree" (16) after eating the (possibly poisoned) apple that grows on it. The apple may be poisonous because it is the child of the speaker's anger—it is sustained and grown via negative emotions, and it's been growing for quite a while.
This poem isn't just about a weird, poisonous tree, though. The poison tree can be seen as a metaphor for what happens when you stay angry for too long a time. Have you ever stewed about something for an extended period of time? Sure you have. We all have. Eventually, though, all that negative energy has to come out, and when it does it's not pretty. Nurturing and feeding anger all the time will eventually end up poisoning somebody, right?
To add another layer to the title, consider that William Blake was a deeply religious man. Much of his poetry should be read with Biblical themes in mind. The idea of a tree that is poisonous recalls the Tree of Knowledge of Good and Evil from the book of Genesis (the first book of the Judeo-Christian bible). In Genesis, God tells Adam and Eve not to eat the fruit of this tree, which they end up doing despite this order. Eating from this tree is the first sin, and as a result, death, pain—in short everything that sucks—enters the world. Blake's title takes a certain cue from this story, and the poem is partly about sin and doing things one shouldn't (like sneaking into a garden to steal an apple or letting one's anger grow and grow).
In the end, the title prepares us for the lesson that will be delivered by the poem's end, and it also identifies the way in which the poem will deliver the lesson. Neat, huh?