Here ‘leprous hide’ refers to the rough bark of a tree, having marks. The ‘leprous hide’ of a tree bears the ‘sprouting leaves’. A leper’s skin is patchy and contains various shades of colour. The bark of a tree is also patchy and has different shades of brown and green. Therefore, the bark of a tree is compared to that of a leper’s skin. In the line mentioned above, the poet ironically suggests that a huge and destructive creature like a tree deserves to be killed brutally.

“But this alone won’t do it.” What is ‘it’? What alone won’t do it? Why?

Here ‘it refers to the act of killing a tree. The poet thinks that hacking and chopping alone will not do it because the injured trunk will heal itself and small green twigs will grow again. The small green twigs if left unchecked will attain its former size. According to the poet, hacking and chopping are not enough to kill a tree because the tree tries to cure the wound caused to it by the greedy section of mankind. Therefore with its healing power, it will repair the damage done to it and will give rise to miniature boughs.