What is "A Poison Tree" about? What is the poet trying to convey?

“The Poison Tree” is a poem about the evil effects of holding anger in. The premise is introduced in the first stanza, in which the poet explains

I was angry with my friend;I told my wrath, my wrath did end.I was angry with my foe:I told it not, my wrath did grow.

The rest of the poem uses language that suggests the story of the Garden of Eden and the fall of...

“The Poison Tree” is a poem about the evil effects of holding anger in. The premise is introduced in the first stanza, in which the poet explains

I was angry with my friend;
I told my wrath, my wrath did end.
I was angry with my foe:
I told it not, my wrath did grow.

The rest of the poem uses language that suggests the story of the Garden of Eden and the fall of man from the Bible to show how nurturing bad feelings can be harmful. The “wrath” that is not told grows and grows until it bears “fruit,” an “apple bright” which tempts his foe and kills him when he eats it (“In the morning glad I see; / My foe outstretched beneath the tree”).

I think Blake is getting at two things here. First, the untold anger leads to the “death” of the foe—in other words, the end of their relationship. Second, and more importantly, is the poet’s “gladness” at seeing his enemy defeated; in harboring the hatred, the poet has turned himself into the serpent in the Garden of Eden story, an agent of destruction, and one who takes delight in harming others. Ultimately the person most harmed by “the poison tree” is the one who created it in the first place.