If we compare the "incomparable," we will discover that the difference of the Japanese garden depends upon the Japanese, very different, attitude toward nature. Two attitudes toward nature are everywhere possible: you confront it or you accept it. This is illustrated in gardens West and East. In the former (think Versailles), nature is but the rawest of materials to do with as you will. Trees are in ordered ranks, paths are straightened, a form is imposed.
In the latter (see any of the 75 Japanese gardens here beautifully photographed), nature is accepted and adopted as a model. But as Charlotte Anderson tells us in her interesting introduction, one of the earliest garden manuals, the 11th-century "Sakuteki," recommends "looking at nature's most beautiful landscapes for inspiration, yet it advises that a garden should reflect nature, not copy it."
Nature is thus not only accepted, it is also naturalized. Just as the flowers in ikebana ("living flowers") are presumed to be more flowerlike than any natural bloom (even though those seen in ikebana are, having been picked, either dead or dying), so the Japanese garden is to be more natural than nature.