A man called Mr. P. has been undone by something a rose seemed to reveal about him. The opening line is odd and intriguing: the rose "told my thoughts," as if a flower had exposed what he'd tried to keep hidden. His response is to drink, and the poem treats this almost like a dinner party, since he "dined with my troubles," as though his worries were guests he sat down with and fed.
The "money horse" is harder to pin down. Judging by the phrasing, it may stand for a gamble, a debt, or a chase after cash that keeps running ahead of him. Then the rose returns at the end, now as the thing that "brought / a slow hell home." What began as something beautiful, perhaps a gift or a memory, ends as a torment he carries into his own house.
The mood is weary, dark and a little wry, much like the blues the title promises. The short lines feel clipped, like a man who has run out of things to say.