“Ash Cactus”, referring to the characteristic ash grey colour of the epidermis of some species in this genus.
A genus of small bushy to shrubby plants, with dense terminal or subterminal branches, producing numerous globose or cylindrical segments which, in some species, appear stacked on top of each other. Roots sometimes tuberous. Leaves tiny, deciduous. Areoles with trichomes, glochids sunk in cavities, and spines sometimes absent.
Flowers diurnal, self-sterile, rotate, appearing at the apex of segments, white or pink, also yellow, orange or red, pollinated by specialized hymenoptera (Alloscirtetica lanosa). Fruits dry or juicy (T. nigrispinus), dehiscent when ripe. Seeds large, irregular, creamy-white to brown, piled up in fruits, embryo comma-shaped, perisperm prominent, light enough to be scattered by the wind, but the seeds of some species are dispersed in the excreta of animals which feed on the fruits (endozoochory) such as chinchillas (Chinchilla brevicaudata, C. chinchilla, the latter unfortunately extinct, Lagidium peruvianum) and guanacos (Llama guanicoe). This fact suggests that we should not blindly trust classification based on seeds, which also adopt a convergence of form.
The genus Tephrocactus grows at the top of or on stony hillslopes, in plains, on sandy, rocky, sometimes schistose soils, in the puna among grasses, usually in full sun, from 250 up to 3800 m in altitude. Tephrocactus is extremely widespread and variable in its habitat.
Argentina (Catamarca, Cordoba, Jujuy, La Rioja, Mendoza, Salta, San Juan, San Luis, Santiago del Estero, Tucuman), Bolivia (Potosi, Chuquisaca), Chile (Tarapaca).
Currently 10 recognised species + one subspecies:
– Tephrocactus alexanderi* (Britton & Rose) Backeb. 1953
– Tephrocactus aoracanthus* (Lem.) Lem. 1868
– Tephrocactus articulatus* (Pfeiff.) Backeb. 1953
– Tephrocactus bonnieae* (Ferguson & Kiesling) Stuppy 2001 (ex Puna bonnieae)
– Tephrocactus geometricus (A.Cast.) Backeb. 1935
– Tephrocactus molinensis* (Speg.) Backeb. 1953
– Tephrocactus nigrispinus* (K. Schumann) Backeb. 1935
– Tephrocactus nigrispinus subsp. atroglobosus (Backeb. ex Guiggi & Palacios) M.Lowry 2012
– Tephrocactus recurvatus* (Gilmer & H.P.Thomas) D.R.Hunt & Ritz 2011 (ex T. curvispinus Backeb. 1963, nom. invai., ex Cumulopuntia recurvata)
– Tephrocactus verschaffeitii* (F.A.C.Weber) D.R.Hunt & Ritz 2011 (ex Austrocyl. verschaffeitii)
– Tephrocactus weberi* (Speg.) Backeb. 1935