In "Pea Bush" by Robert Frost, was the speaker free to be poetical and why?
One must trust in the fact that all speakers have the right to be poetical. People only fail to be poetical when they choose to close their minds to the beauty of the world and not experience it from a state which highlights and embodies imagination and emotion.
In Frost's poem "Pea Bush," the speaker is almost certainly Frost himself. Frost enjoyed (assumed based upon critical research and critical analysis of him and his work) nature. He reveled in nature. He felt saddened and uplifted by nature. Nature provided the music which accompanied his poetic voice.
Therefore, the speaker was free to be poetical based upon the fact that no one could really stop him. Regardless of what others may have thought, regardless of what others may have said (regardless of the lack of dialogue or other voices), the speaker was able to regard nature with a poetic imagination and voice.