The speaker is outside among the leaves, probably in spring or summer, and decides to write a rhyme for winter because that season gets no songs. He talks to winter as if it were a person who feels left out, telling it not to be afraid: when the leaves fall, it will have an icy crown. That image is beautiful but also a little playful, making the cold season sound royal rather than bleak. Even though the buds are still on the trees, he is already thinking ahead to the end of the year. He offers winter his song now, and trusts that winter will sing back to him later. The mood is gentle, reflective, and quietly hopeful, treating the changing seasons as a kind of friendship.
In Green Ways — Summary
Among the leaves I make a rhyme, To the winter in its pall, For the poor, forgotten time Has not had a song at all.
Winter ! winter ! do not fear. You shall have an icy crown At the falling of the year. When the leaves have tumbled down.
I am singing to you here, Though the bud is on the tree, At the falling of the year You will sing a song to me.