Xerophyte

Roots

Napiform.

Note

This member of the Cactaceae family was named after the Argentine province of La Rioja.

Flowers

Apical up to 50 mm tall, and 40 mm in diameter. Pericarpel 15-20 mm long, olive-green to glaucous-green, the scales widely edged with white and with a pink point, passing gradually to the external tepals. The latter spatulate, white to rosy white, with an olive-green wide median band. Internal tepals lanceolate, white with a pink central line and carmine base. Throat dark carmine. Filaments pale green; anthers sulphur-yellow. Style greenish white with a pink base. Stigma yellowish white, with 9-12 lobes, between the primary and secondary stamens.

Spines

3-5(-7) all radials, straight, overlapping, up to 15 mm long. Young spines light brown to blackish-brown, passing then to light grey with a dark point. Central spines absent.

Ribs

10-16, vertical, straight, rather acute, divided into conical tubercles with conical chins, separated by very apparent V-shaped transverse furrows.

Stem

Flattened-globose, grey-green, olive green, greenish-brown to chocolate, 5-8 cm tall and 8-11 cm in diameter. Apex depressed, spineless, woolly.

Areoles

Oval, 3 × 4-5 mm, with yellowish felt, becoming greyish, then naked.