Name and species circumscription
Austrocactus nobilis is the name accepted in Plants of the World Online, checked on 10 October 2026. The combination Austrocactus bertinii subsp. nobilis also appears in the literature. The 2025 revision retains species rank and places it in section Coxiani. [2-WWW] [Böhnert et al. 2025, taxonomic record and species description in the 2025 revision]
Large tubercles and strong spines
The plant branches and forms a clump with age. Stems are upright or spreading, cylindrical to columnar, 10–40 cm long and 3.5–9 cm in diameter. The epidermis is green, with a reddish tint in sunlight. Nine to eleven ribs divide completely into large, prominent tubercles. Oval areoles measure around 8 × 10 mm and have short beige or grey felt. [Böhnert et al. 2025, p. 411]
Four to six central spines are very strong, awl-shaped and almost straight, with a thickened base and surface coating. Up to twenty needle-like radial spines lie in pairs, mostly horizontally. Their large number, together with the massive central spines and tubercle size, is among this species' distinguishing features. [Böhnert et al. 2025, p. 393, 411]
The flower and woolly fruit
The bowl-shaped flower measures around 7 cm long and 6.5 cm in diameter. The lanceolate tepals are pointed, pale yellow in the lower part and pink to brownish red above. The style is carmine red, and the stigma has 11–14 dark purple lobes. The green pericarpel is densely covered with soft white hairs. [Böhnert et al. 2025, p. 411]
The barrel-shaped fruit is 1.5–2 cm long and 2–3 cm in diameter. It is dark green, covered with white wool and thin bristles. As it ripens, it dries and opens from the base. The brownish-black seeds are curved and measure around 1.6 × 2.2 mm. [Böhnert et al. 2025, p. 411]
Growth form dependent on the growing site
The species was described from the plateau north of Ingeniero Jacobacci in Río Negro Province. It occupies granite grit and rock fissures. Plants growing in fissures were smaller and had fewer stems than those on flatter ground, which reached substantial sizes. The revision documents this variation within one species. [Böhnert et al. 2025, p. 411]
In the genomic trees, A. nobilis lies close to A. coxii and A. occidentalis, but principal component analysis of the markers shows more complex relationships. The authors consider possible gene flow with other lineages of the genus. This position indicates a need for additional population studies, while retaining a well-recognisable set of morphological features. [Böhnert et al. 2025, p. 389–391, 407, 411]
Related articles
Synonyms and names in the literature
Austrocactus bertinii subsp. nobilis [2-WWW]