Yucca is a genus of about fifty species. However, any two can hybridize. They are more like fifty or so varieties of one species. They maintain distinction by blooming at different times or inhabiting different ranges. Mound lily, Yucca gloriosa, is one of these species. However, it is technically a perpetuating hybrid of Yucca filamentosa and Yucca aloifolia.
Mound lily develops symmetrical foliar rosettes that are only a few feet tall. Stout trunks that develop below can very slowly elevate these rosettes about eight feet. Elegantly tall floral stalks can stand as high as five feet higher. The stiff and evergreen leaves are one to two feet long, and about two inches wide. Their terminal foliar spines are very sharp.
The most popular cultivar of mound lily is variegated with creamy white stripes. Tristis is a variety with more flexible and arching foliage. It formerly classified as a distinct species of Yucca recurvifolia. All yuccas bloom with small, pendulous and creamy white flowers. Such flowers may exhibit a pale purplish or faint pale greenish blush.