The Pogo book by Walt Kelly that includes the poem "Spring has sprung, The grass riz, I wonder where flowers is?" is
"Pogo – The Complete Pogo Comic Strip Volume 1: The Early Years 1948-1950".
The poem, often misattributed to Ogden Nash, was first published in the Pogo comic strip on March 8, 1949. It quickly became a popular and recognizable piece of the strip's humor.