This poem sounds like a Mad Lib filled out by someone who had just watched the Popeye cartoon:
The first of the (adjective) messages read: "(name) sits in (place),
Unthought of. From that (noun) of an apartment,
From (adjective) curtain's (noun), a (noun) emerges: a country."
Well, at any rate, it's a Mad Lib written by someone who uses strange sentence structures. Parts of the poem are as close to Lewis Carroll's idea of "Jabberwocky" as possible without writing complete nonsense. The poem's language is a hodge-podge of words and phrases that stick out like so many sore thumbs. Like a Md Lib, the poem reads grammatically correct, like a paragraph written in standard English prose. But Ashbery mixes in many different kinds of speech, from old patriotic songs ("For this is my country") to every day slang ("I'm taking the brat to the country") to philosophical reflections ("rupturing the pleasant arpeggio of our years") to child-like rhyming ("musty gusty evening"). The names are similarly ridiculous: the Sea Hag? Swee'pea? Alice the Goon? Then again, they have the virtue of being the real names from Popeye.
The repetition of words like "strange" and "spinach" forces Ashbery to use these words in different contexts and with different meanings to keep the poem varied. Part of the reason that the poem does not have many pauses at the end of lines is to make these words less visible. The entire poem has the tone of matter-of-fact rambling of a Mad Lib: pretty (adjective), huh?