In my opinion, the title can not help you understand the meaning of the poem because the title is a question that someone or the author is trying to answer.
The author uses imagery to help you picture what she is saying in the poem that makes you create an image in your head of the wind. The poem also includes one of the five sense, which is sight, that she uses in the title as well as throughout the poem to explain to the readers that wind cant be seen but its effects can be seen and felt.
I think the poem literally means what it is saying, and this is where there is figurative language included because it says, "but when the trees bow down their heads." This means the author was using personification and that was signifying that the wind is strong or that there is a power blowing on the tree branches.
The author used repeating phrases such as, who has seen the wind? and neither you nor I. So overall, my interpretation of the poem is that there is a natural strong force trembling the leaves and making the tree bow down