Hesperoyucca

Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Monocots
Ordo: Asparagales

Familia: Asparagaceae
Subfamilia: Agavoideae
Genus: Hesperoyucca
Species: H. newberryi – H. whipplei
Name

Hesperoyucca (Engelm.) Baker, Rep. (Annual) Missouri Bot. Gard. 4: 208. (1893)

Type species: Hesperoyucca whipplei (Torr.) Baker ex Trel., Rep. (Annual) Missouri Bot. Gard. 4: 208 (tt. 16, 23). (1893)

Synonyms

Basionym
Yucca [infragen.unranked] Hesperoyucca Engelm.

References

Baker, J.G., 1892. Bulletin of Miscellaneous Information, Royal Gardens, Kew (61): 8, in obs
Baker, J.G., 1893. Report (Annual) of the Missouri Botanical Garden 4: 208.
Govaerts, R. et al. 2019. Hesperoyucca in World Checklist of Selected Plant Families. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the internet. Accessed: 2019 Jan. 9. Reference page.
International Plant Names Index. 2019. Hesperoyucca. Published online. Accessed: Jan. 9 2019.

Hesperoyucca is a small genus of two recognized species of flowering plants closely related to, and recently split from, Yucca, which is in the century plant subfamily within the asparagus family.[2]
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.[3] Hesperoyucca is also distinct in DNA analysis. The genus is native to Mexico and the southwestern United States.[4]

Species[5][6]

Hesperoyucca newberryi (McKelvey) Clary (syn. H. whipplei subsp. newberryi, Yucca newberryi ) - northwestern Arizona
Hesperoyucca peninsularis (McKelvery) Clary (syn. Yucca whipplei ssp. eremica) – peninsular candle – Baja California, Baja California Sur
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.[3][7] 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]).[3]

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 recognising Hesperoyucca as being at the same rank as, but separate from, Yucca.[3][8] It has taken recent DNA analysis to confirm that they are indeed genetically distinct from Yucca.[3]

The splitting of Hesperoyucca from Yucca is still not widely reflected in available literature or online (for example, the British Royal Botanic Gardens, Kew and the Royal Horticultural Society websites do not recognise the name as current).[9][10]
References

Tropicos, Hesperoyucca (Engelm.) Baker
Stevens, P.F., Angiosperm Phylogeny Website: Asparagales: Agavoideae
Agavaceae.com – page includes a key toYucca and the three recognised species of Hesperoyucca
Flora of North America, Vol. 26 Page 439, Hesperoyucca (Engelmann) Baker, Bull. Misc. Inform. Kew. 1892: 8. 1892.
Kew World Checklist of Selected Plant Families
Clary, Karen Husum. 2001. The genus Hesperoyucca (Agavaceae) in the western United States and Mexico: New nomenclatural combinations. Sida 19(4): 839-847.
Flora of North America: Hesperoyucca
IPNI International Plant Names Index
RBG Kew search results for Hesperaloe[permanent dead link]
online Plant Finder RHS Royal Horticultural Society