Shift in the Words - The Problem with Describing Trees

In the poem "The Problem of Describing Trees" by Robert Hass, he switches his argument about midway through the poem, "And the tree danced. No. The tree capitalized". The beginning of his poem is describing specifics points about a tree; the aspen glitters in the wind, the leaf flutters protecting the cells drying out in the heat if summer, while the ending of the poem contradicts itself saying that language has limits to describing a tree, or anything within poetry.

I think the author was trying to show how important language is and how it can be changed. Especially when the author writes, "It is good sometimes for poetry to disenchant us", he shows that language can be interpreted in many ways by a reader as well as a writer.