Which flower is specifically recognized as a filler flower in floral arrangements?

Baby's breath, scientifically known as Gypsophila, is widely recognized as a filler flower in floral arrangements due to its delicate, small white blossoms and airy appearance. This characteristic makes it perfect for adding volume and a soft touch to bouquets without overwhelming the main flowers. The lightweight nature of Baby's breath provides a subtle background that enhances the overall aesthetic of arrangements, allowing the focal flowers to stand out while still contributing to the overall balance and texture.

In contrast, the other options listed are typically used as main or focal flowers. Carnations are valued for their robust blooms and can hold their own in an arrangement, making them a primary flower rather than a filler. Zinnias are known for their larger, vibrant colors, serving as centerpieces in many designs. Chrysanthemums have a fuller form and are similarly recognized for their prominent role in arrangements, often acting as focal points. Each of these flowers has distinct characteristics that make them integral to floral compositions, but Baby's breath specifically serves the unique role of a filler flower.