Which foliage type is known for having light, feathery leaves and is commonly used as a filler?

The correct choice is Bear grass. This foliage type is characterized by its light, feathery leaves, which give it a delicate appearance. Bear grass is often utilized in floral arrangements as a filler because its texture adds depth without overwhelming the overall design. Its airy nature allows it to complement various flowers and other foliage, enhancing the visual balance of the arrangement.

While eucalyptus also has its own aesthetic appeal and is used in arrangements, it typically features thicker, more substantial leaves compared to the lightness of Bear grass. Emerald, known for its rich green foliage, does not possess the feathery quality and is usually utilized for its more substantial visual impact. Aspidistra is known for its broad, sturdy leaves, which again do not align with the light and feathery characteristic sought in this question.