Which type of flowers are referred to as primary flowers for establishing the skeleton outline of an arrangement?

Line flowers are essential in floral design as they help to establish the skeleton outline of an arrangement. These flowers typically have long, linear shapes and are used to create height and structure within the arrangement. They serve as the framework that helps to guide the eye through the composition, establishing the overall shape and providing a sense of movement.

Using line flowers effectively sets the stage for other types of blooms within the arrangement, allowing mass flowers to fill in the volume and filler flowers to soften the composition. This hierarchical structure is crucial in floral design, as it ensures that the arrangement has balance, symmetry, and visual interest. The characteristics of line flowers make them indispensable for achieving a well-structured floral design.