Acanthocalycium leucanthum

Acanthocalycium leucanthum is a species of flowering plant in the cactus family Cactaceae from Argentina.

Description
Acanthocalycium leucanthum usually grows singly, but occasionally forms small groups. The spherical to short cylindrical, gray-green shoots reach heights of up to 35 cm (rarely up to 80 cm) with diameters of 12 cm. There are twelve to 14 blunt ribs that are slightly notched. The elongated areoles on them are yellowish white and are 1 to 1.5 cm apart. The single thick, brown central spine is curved upwards and 5 to 10 cm long. The eight to ten yellowish-brown marginal spines are curved and slightly twisted. They are up to 2.5 cm long.

The long, funnel-shaped, white, occasionally slightly pink flowers appear on the upper parts of the shoots and open at night. They are up to 20 cm long. The spherical to elongated, fleshy fruits are greenish red to deep red.

Distribution
Acanthocalycium leucanthum is widespread in northwest to central Argentina from sea level to altitudes of 1000 meters.

Taxonomy
The first description as Echinocactus leucanthus by Joseph zu Salm-Reifferscheidt-Dyck was published in 1834. The specific epithet leucantha is derived from the Greek words leukos for 'white' and anthos for 'flower' and refers to the flower color of the species. Boris O. Schlumpberger placed the species in the genus Acanthocalycium in 2012. Further nomenclature synonyms are Cereus leucanthus (Gillies ex Salm-Dyck) Pfeiff. (1837) and Echinopsis leucantha (Gillies ex Salm-Dyck) Walp. (1843)