This analysis of the Whirl-Blast, by Wordsworth, could not be less accurate:
"A Whirl-Blast From Behind the Hill" is a poem alive in every sense—fresh language, quick iambic rhythms, startlingly original conception.
John Mahoney, William Wordsworth: A Poetic Life, p.83
Lines like these would be rejected even at college level:
I sate within an undergrove
Of tallest hollies tall & green
A fairer bower was never seen
There are, by my count, only three original conceptions in the poem:
And of these, only the last is especially original. It also forms the main motivation for writing, in spite of Wordsworth's initial argument that it was a "pleasant sight".
One characteristic does rescue the poem: it is from the stratum of the Lyrical Ballads, the start of the Romantic poetry movement in England. It is, to delve into the actual point, a real experience.
Rousseau, confessing to steal silver spoons he had really stolen, is much more interesting than one of Dostoevsky's people confessing to an unreal murder.
James Joyce, quoted in Budgen, p.184
Something being real in poetry makes it special because it situates the experience, making it part of a much richer story than an isolated poem.
Dorothy Wordsworth writes of the same event in her journal:
18th March 1798: The Coleridges left us. A cold, windy morning. Walked with them half way. On our return, sheltered under the hollies during a hail-shower. The withered leaves danced with the hailstones. William wrote a description of the storm.
She captures only the essential points in her account. She calls the bower "the hollies" as though she were already familiar with them, and sure enough there is at least one prior instance of them apparently retreating to the same shelter:
31st January 1798: Set forward to Stowey at half-past five. A violent storm in the wood; sheltered under the hollies.
This gives us new information which we could not have learned from William's poem, and which could not have been found about a product of the imagination alone.
When Dorothy describes these events, she talks about even William's poem from the outside, though using the same kind of language. William describes a return visit to the bower, 42 years later,[1] in terms that seem wistful of his prior creativity.
Dorothy's Alfoxden Journals are very rich, and both Coleridge and Wordsworth used her observations in their poems. At times, she is nearly as rich in creative thought as the best lines of Milton.
William's poem about the wider Whirl-Blast story, then, is beautiful—but not for the reasons enthusiastically suggested by Mahoney. To make the story more exciting, the poets could have described it on more occasions, adding more aspects of description and imagination with each telling.
(Footnote: [1] Wordsworth says 41 years, but he also dates the poem incorrectly to 1799 rather than 1798. In light of that, 42 years later, 1840, is more likely.)