Answer & Explanation:
'The Heart of Tree' poem is written by Henry Cuyler Bunner. The poem although looks like appreciating trees for their important role in life on earth. But the title has metaphor in it. It rather highlights greatness of man who plants a tree.
These various kinds of men's achievements related to trees have been highlighted : Men maintain ecological & environmental balance by planting trees. Men plant trees & help future generation's environment sustainability.