Quest - sf68 ( Poul Anderson)

In a future where all of nature is synthetic, Harry Johnson, a weary urbanite, grows curious about the idea of "real".

Harry leaves the sprawling automated city in his air-car, seeking genuine nature. Eventually, he stumbles upon a hidden green park—a vivid oasis filled with grass, birds, and fresh air, a stark contrast to his sterile surroundings

Harry marvels at the park’s life, he wonders who tends it. His discovery reveals it's maintained—and created—by an aging, solitary gardener assisted by robots.