Subspecies, varieties, forms and cultivars of plants belonging to the Yucca rostrata group

• Yucca rostrata Engelm. ex Trel.: larger-growing (3-3.5 m high) with larger inflorescences, longer and broader leaves with the widest part considerably above the middle, and smooth on both faces. Distribution: SW Texas and Mexico (Chihuahua and Coahuila).
• Yucca thompsoniana Trel.: smaller-growing (1-2 m high) with rough-feeling, smaller inflorescences, shorter and narrower leaves widest at or above the middle and somewhat scabrous on both faces. Distribution: Texas and N. Mexico (Chihuahua, Nuevo leon and Coahuila).