Name and species circumscription
Austrocactus subandinus is the name accepted in Plants of the World Online, checked on 10 October 2026. [2-WWW]
Spreading stems and two groups of radial spines
The plant branches, forming spreading cylindrical stems up to 18 cm long and 5.5 cm in diameter. They are green to dark green. Usually eight ribs divide into small, rounded tubercles. Oval areoles initially have sparse pale felt, which quickly disappears. [Böhnert et al. 2025, p. 407]
There are at most five central spines. One projects forwards, and the longest curves towards the stem tip. They are finely hairy and awl-shaped. Among the radial spines, up to seven stronger ones and around eight very thin ones were described. The thin ones are paired, translucent and needle-like. This combination distinguishes the species from A. decorus, with its more numerous strong central spines and strong radial spines. [Böhnert et al. 2025, p. 394, 401, 403, 407]
A yellow flower and dry fruit
The funnel-shaped flower measures around 5 cm long and 5.5 cm in diameter. The tepals are spatulate with a short point, yellow in the lower part and distinctly darker in the upper third, sometimes reddish brown. The style is white to pale pink, and the 10–14 stigma lobes are yellowish to greenish. The pericarpel has bristles, hairs and very little wool. [Böhnert et al. 2025, p. 407]
The barrel-shaped fruit is around 1.5 cm long and 2 cm in diameter. It is dark green, with scales, bristle-like hairs and white wool. On ripening, it dries and opens from the base. The blackish-brown seeds are curved and measure around 2.5 × 2 mm. [Böhnert et al. 2025, p. 407]
Limestone sites in Malargüe
The revision describes the species as endemic to the Malargüe department of Mendoza Province, occurring at elevations of 1900–2500 m, often on limestone rocks. The authors highlight tolerance of limestone substrate as their own field observation within the genus. They did not conduct an experiment comparing growth on substrates of different pH. The natural site therefore describes habitat, without an established recipe for a potting mix. [Böhnert et al. 2025, p. 407]
In the genomic analyses, the species was sister to the shared lineage of A. decorus and A. hibernus, with strong support for this relationship. Their shared pale stigmas and sparse fruit coverings place these plants in the revision's section Hiberni. The dry fruits of A. subandinus retain a difference from the succulent fruits of A. hibernus. [Böhnert et al. 2025, p. 401, 403, 406–407]