The poet symbolizes a tree as a deep-rooted evil. This symbolism is evident in the poem's portrayal of the tree as a negative force that brings destruction and suffering.

Firstly, the poem describes the tree as being "hung with useless light," suggesting that it is adorned with artificial and deceptive qualities. This can be seen as a metaphor for evil, which often disguises itself as something attractive or desirable.

The poem further emphasizes the negative connotations of the tree by describing it as a "blackened stump." The use of the word "blackened" implies that the tree is corrupted and devoid of any positive qualities. This imagery is consistent with the portrayal of evil as something dark and malevolent.

Additionally, the poem describes the tree as being "bent like a crooked arm." This suggests a sense of deformity and unnaturalness, further reinforcing the notion of the tree as a symbol of evil. The crooked arm imagery also implies a sense of aggression or harm, as if the tree is reaching out to cause damage.

Furthermore, the poem portrays the tree as being "a giant with poison in his veins." This imagery suggests that the tree is not only evil in itself, but that it also possesses the ability to spread its malevolence to others. This reinforces the idea that the tree is a symbol of deep-rooted evil, with its poison representing the destructive influence it has on the world around it.

In conclusion, the poet symbolizes a tree as a deep-rooted evil in the poem. Through vivid imagery and metaphorical language, the poem portrays the tree as a negative force that brings destruction and suffering. The tree's artificial light, blackened stump, crooked arm, and poisonous veins all contribute to its symbolism as a symbol of evil.