As a result, this species exhibits much variation in growth habit, general ecology, reproductive strategies, phenology, and gross morphology. Yucca whipplei ssp. Yucca whipplei ssp. Webber Yucca whipplei ssp. Very little is known about morphological characteristics used to delineate these groups.
Controversy still surrounds the five most widely recognized subspecies.
Clearly, much more research is needed to fully document variation of this species and to determine appropriate taxonomic relationships. Tirmenstein, D. A. 1989.