What characteristic defines the visual impact of mass flowers in an arrangement?

The characteristic that defines the visual impact of mass flowers in an arrangement is their abundance and density. Mass flowers are typically large, bold blooms that are used to fill out designs and create a substantial visual presence. The way they cluster together enhances the overall fullness and richness of the arrangement, drawing the eye and providing a sense of volume. This density contributes to the dramatic and lush feel that mass flowers bring, making them a prominent feature in floral design.

In contrast, other aspects like colorful appearance and architectural form, while possibly relevant to specific designs, do not inherently define the impact of mass flowers. Additionally, fragility does not align with the concept of mass flowers, as they are often chosen for their robustness and ability to hold up well in arrangements. Thus, the concept of abundance and density is what best encapsulates the defining visual impact of mass flowers.