How do varied empty spaces make a flower arrangement silhouette more interesting?

In the context of floral decoration, the silhouette—or outline—of an arrangement is considered most interesting when the empty spaces within the composition vary in both size and shape.

By incorporating varied spaces, a designer avoids the restricted, static quality often found in evenly shaped or uniform contours, such as simple pyramids or mounds. This variation contributes to a more dynamic and aesthetically pleasing design, preventing the outline from appearing overly contrived. To further enhance the sculptural quality and depth of the arrangement, designers may also manipulate plant materials to extend forward or recede, and turn flower heads in different directions to break up contour uniformity and draw the viewer's eye into and around the composition.1