Scientific taxonomy article
Accepted name and nomenclatural basis
The current Kew backbone accepts this species as Tephrocactus geometricus (A.Cast.) Backeb.1 The International Plant Names Index records the same combination under LSID urn:lsid:ipni.org:names:250216-2, published on page 111 of Backeberg and Knuth's Kaktus-ABC in 1936.2 Its basionym is A. Castellanos's 1934 name Opuntia geometrica.12
That history matters because Tephrocactus alexanderi subsp. geometricus is a later combination based on the same type. In the current Kew backbone it is not an independently accepted taxon; it is a synonym of T. geometricus.1
Systematic position and species concept
In the live production tree the species sits directly below the genus Tephrocactus within tribe Tephrocacteae. Kew confirms placement in family Cactaceae and order Caryophyllales.1 A 2019 molecular, morphological, and cytogenetic study recovered Tephrocactus as monophyletic and recognized T. geometricus as a distinct species rather than collapsing it into neighboring names.3
This page updates only the species level. Existing Tephrocactus, Tephrocacteae, Opuntioideae, and Cactaceae nodes remain outside the payload and are not regenerated.
Native range and habitat
Plants of the World Online gives the native range as Catamarca, Argentina and places the species in the Argentina Northwest floristic region.1 It is recorded as a succulent subshrub growing primarily in desert or dry shrubland.1 That native-range evidence is distinct from the commercial plant's production origin in Adana.
Limits of morphological interpretation
The 2019 Tephrocactus study evaluates growth form, leaves, glochids, and floral characters together with molecular and cytogenetic evidence when reconstructing relationships in the genus.3 Identification should therefore not be reduced to a trade name or a single photograph. Segment form, visible armature, and growth pattern in cultivation can be influenced by growing conditions, and a product photograph is not a taxonomic voucher.
Conservation evidence
This editorial review did not verify a maintained IUCN Red List assessment tied directly to the currently accepted T. geometricus species concept. The existing live LC value is therefore not inherited from another Tephrocactus taxon or from a broader historical concept and will be cleared. Absence of verified species-level evidence is not converted into an invented threat category.
Synonymy
The 2026 Kew species page lists exactly two synonyms and classifies both as homotypic: Opuntia geometrica A.Cast. and Tephrocactus alexanderi subsp. geometricus (A.Cast.) Guiggi.1 These names document nomenclatural history; the canonical species page follows the accepted combination Tephrocactus geometricus.
References
- Plants of the World Online. “Tephrocactus geometricus (A.Cast.) Backeb.” Royal Botanic Gardens, Kew. Accessed: 2026-08-09. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:250216-2 ↩
- International Plant Names Index. “Tephrocactus geometricus (Castell.) Backeb.” Accessed: 2026-08-09. https://www.ipni.org/n/250216-2 ↩
- Las Peñas, M. L., Kiesling, R. & Bernardello, G. “Phylogenetic reconstruction of the genus Tephrocactus (Cactaceae) based on molecular, morphological, and cytogenetical data.” Taxon 68(4). https://doi.org/10.1002/tax.12092 ↩
