John Ashbery, 90, an enigmatic genius of modern poetry whose energy, daring, and boundless command of language raised American verse to brilliant and baffling heights, died Sunday.

Mr. Ashbery, winner of the Pulitzer Prize and often mentioned as a Nobel candidate, died at his home in Hudson, N.Y., of natural causes, said his husband, David Kermani.

Few poets were so exalted in their lifetimes. Mr. Ashbery was the first living poet to have a volume published by the Library of America dedicated exclusively to his work. His 1975 collection, Self-Portrait in a Convex Mirror, was the rare winner of the book world's unofficial triple crown: the Pulitzer Prize, the National Book Award, and the National Book Critics Circle prize. In 2011, he was given a National Humanities Medal and credited with changing "how we read poetry."

Among a generation that included Richard Wilbur, W.S. Merwin, and Adrienne Rich, Mr. Ashbery stood out for his audacity and for his wordplay, for his modernist shifts between high oratory and everyday chatter, for his humor and wisdom, and dazzling runs of allusions and sense impressions.

"No figure looms so large in American poetry over the past 50 years as John Ashbery," Langdon Hammer wrote in the New York Times in 2008. "Ashbery's phrases always feel newly minted; his poems emphasize verbal surprise and delight, not the ways that linguistic patterns restrict us. "

But to love Ashbery, it helped to make sense of Ashbery, or least get caught up enough in such refrains as "You are freed/including barrels/heads of the swan/forestry/the night and stars fork" not to worry about their meaning. Writing for Slate, the critic and poet Meghan O'Rourke advised readers "not to try to understand the poems but to try to take pleasure from their arrangement, the way you listen to music." Writer Joan Didion once attended an Ashbery reading simply because she wanted to determine what the poet was writing about.

"I don't find any direct statements in life," Mr. Ashbery once explained to the Times in London. "My poetry imitates or reproduces the way knowledge or awareness comes to me, which is by fits and starts and by indirection. I don't think poetry arranged in neat patterns would reflect that situation." - AP