Introduction
Yuccas are wonderful rosette plants related to Agaves–both are members of the Liliaceae. The Liliaceae family contains many types of plants, including familiar garden bulbs. All Liliaceae flowers have three petals and three sepals.
The Details
Yuccas are characterized by stiff, pointed leaves. However, a few species (e.g., Y. gloriosa) have softer leaves. The plants may have trunks or they may be without trunks and form a rosette of leaves directly on the soil. Some yuccas, such as Y. aloifolia, are considered weeds in some coastal areas where they create Yucca thickets/forests near the surf. While considered western plants, a few yuccas (such as Y. filamentosa) are native to the eastern states.
Yucca flowers have evolved an amazing relationship with yucca moths. Yucca flowers need the moth to pollinate them; this is an obligate step, and other insects just cannot do it correctly. In reward for pollinating the Yucca, the moth bores a hole into the side of the infant seed capsule and deposits eggs. The developing moth larvae feed on some (but not all) of the growing Yucca seeds. Everybody wins because the moth larvae are fed and because the Yucca still has enough seeds to scatter on the wind.
Additional Reading: Yucca Moth and Yucca Coevolution
(Photo = Yucca sp, Michael Real)