Question

what message does the poet want to convey through the poem on killing a tree

Answer 1

The poet in this poem symbolizes deep-rooted evil.  

He tells that trees can’t be killed out by hacking and chopping it.  

To give a permanent end it should be uprooted fully and left out in the sun.  

Same way social evil can’t be eradicate by criticising them.  

Society should root them up to kill forever.

Answer 2

The primary topics of the ballad "On Killing A Tree" are:

To make another mindfulness in the psyches of individuals that trees are as much living animals as creatures.

To mirror the desperation with which steps should be taken to moderate nature, so as to guarantee that the Earth remains an inhabitable planet that can support Life.