Hesperoyucca is a small genus of two recognized species of closely related to, and recently split from, Yucca, which is in the Agavoideae within the Asparagaceae.
Description
Hesperoyucca is distinct from
Yucca in having loculicidally dehiscent
fruit and a scape more than 2.5 cm diameter with reflexed (not erect) bracts. The stigma is capitate, whereas those of
Yucca split into three reflexed lobes. The glutinous
pollen is released in a sticky mass; that of
Yucca species is released as single grains.
[ Agavaceae.com – page includes a key to Yucca and the three recognized species of Hesperoyucca] The genus is native to
Mexico and the southwestern
United States.
[ Flora of North America, Vol. 26 Page 439, Hesperoyucca (Engelmann) Baker, Bull. Misc. Inform. Kew. 1892: 8. 1892. ]
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Hesperoyucca newberryi (McKelvey) Clary (syn. H. whipplei subsp. newberryi, Yucca newberryi ) - northwestern Arizona
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Hesperoyucca peninsularis (McKelvery) Clary (syn. Yucca whipplei ssp. eremica) – peninsular candle – Baja California, Baja California Sur
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Hesperoyucca whipplei (Torr.) Trel. (syn. Yucca whipplei) – chaparral yucca, our Lord's candle or Spanish bayonet – southern California, Baja California
Taxonomy
The taxonomy of
Hesperoyucca is complex and somewhat controversial.
[ Flora of North America: Hesperoyucca] Originally, in 1871, George Engelmann ranked "Hespero-Yucca" as a section of Yucca (with only one member, Yucca whipplei; all other Yucca species he placed in section Eu-Yucca, with three subgroups). In 1895 he revised his classification of Yucca, to four equal groups, of which Hesperoyucca was one. In 1876, John Gilbert Baker gave it the rank of subgenus; in 1892 he noted that it "had better be kept as a genus distinct from Yucca" (but actually retained the name Y. whippleii sic).[
]
Some authorities accept this as having erected the genus Hesperoyucca, but others credit this to William Trelease, who printed a taxonomic description in 1893, formally recognizing Hesperoyucca as being at the same rank as, but separate from, Yucca.[ IPNI International Plant Names Index] It has taken recent DNA analysis to confirm that they are indeed genetically distinct from Yucca.[
]
The splitting of Hesperoyucca from Yucca is still not widely reflected in available literature or online (for example, the British Kew Gardens and the Royal Horticultural Society websites do not recognize the name as current).[ RBG Kew search results for Hesperaloe][ online Plant Finder RHS Royal Horticultural Society]
