A few of the fifty or so species of Yucca go by the names of Spanish bayonet or Spanish dagger. Both common names apply to Yucca gloriosa. However, only this single species is also the mound lily. Most other Spanish bayonet and Spanish dagger are from deserts or chaparrals. Mound lily is from southeastern North America, so likes periodic watering.
If that is not confusing enough, the curved leaf yucca, which had been Yucca recurvifolia, is now Yucca gloriosa var.(iety) tristis. It has distinctly pliable leaves with a matte surface texture, and is rarely variegated. Mound lily has stiffer and smoother leaves that are more likely to be variegated. It had been rare, but is becoming one of the more popular yuccas.
Although it does not grow fast, and takes many years to form stout trunks, mound lily can eventually get taller than six feet. Taller floral panicles rise above the densely evergreen foliage. The small and pendulous flowers are pale white, perhaps blushed with brownish purple and pink. The leaves are about a foot or two long and maybe three inches wide, with very sharp terminal spines.