1. Hesperoyucca whipplei (Torrey) Trelease, Rep. (Annual) Missouri Bot. Gard. 4: 208. 1893.
Yucca whipplei Torrey in J. C. Ives, Rep. Colorado R. 4: 29. 1861; Hesperoyucca whipplei var. graminifolia (Alph. Wood) Trelease; Yucca californica Groenland; Y. graminifolia Alph. Wood; Y. nitida C. Wright ex S. Watson; Y. ortgensiana Roezl ex Ortgies; Y. whipplei subsp. caespitosa (M. E. Jones) A. L. Haines; Y. whipplei var. caespitosa M. E. Jones; Y. whipplei subsp. intermedia A. L. Haines; Y. whipplei var. intermedia (A. L. Haines) J. M. Webber; Y. whipplei subsp. parishii (M. E. Jones) A. L. Haines; Y. whipplei var. parishii M. E. Jones; Y. whipplei subsp. percursa A. L. Haines; Y. whipplei var. percursa (A. L. Haines) J. M. Webber
Plants monocarpic or polycarpic, sometimes rhizomatous, some with secondary rosettes at base or stems branching to form new rosettes after flowering; rosettes single or cespitose, in small to very large, compact or open communities, or occasionally solitary. Leaves 20–90(–125) × 0.7–2 cm wide at base in narrow forms, 2–2.5 cm in broader forms. Scape 0.9–3 m × 2.5–15 cm diam. near base. Inflorescences 1 when rosette solitary, 1–many per rosette when rosettes in colonies, 2.5–28 × 1.5–7 dm at widest point. Capsules with conspicuous placental wings at maturity.
Flowering spring. Desert, chaparral, desert woodland coastal sage; 300--2500 m; Calif.; Mexico (Baja California).
Within Hesperoyucca whipplei, W. Trelease (1893) recognized two varieties, A. L. Haines (1941) and P. A. Munz (1959) each recognized five subspecies, and J. M. Webber (1953) recognized four varieties based on growth form. Others (S. D. McKelvey 1938–1947; K. K. McKinney and J. C. Hickman 1993) have argued that growth form in this species is highly variable, and have questioned the desirability of recognizing any infraspecific taxa at all in H. whipplei.
Haines, A. L. 1941. Variation in Yucca whipplei. Madroño 6: 33–45.