Description: Solitary, flattened globose cactus
Stem: Sub-globose to depressed globose, up
to 35 mm wide and up to 15 mm tall.
Ribs: Divided into tubercles, arranged in 5 and 8 spirals with 3
or 4 tubercles per spiral, dull medium green, up to 5 mm high, rhomboidal
and up to 10 mm wide at base, conoidal.
Areoles: About 1 mm long, copiously woolly with thick, long,
white wool in youth, soon becoming bare
Spines: 6 to 7, and occasionally with an additional upper
(sub-central) spine, glassy white with blackish tip, slender acicular,
relatively stiff and slightly recurved, spreading, radiating; lower
three spines up to 5 mm long, upper lateral spines
up to 7 mm long, upper
spine (s) ca. 18-22 mm long and generally incurved, connivent over the
top of the stem, or occasionally erect to somewhat tortuous;
Flowers: White or pink, 35 mm wide, ca. 18 to 25 mm long;
perianth segments with a slightly darker pale pink or pale tan
middle-stripe; outer segments with a brownish middle-stripe on the outer
surface; style white to pale cerise with 3 to 6 whitish stigma lobes
which overtop anthers; stamens numerous with pale cerise filaments and
golden yellow anthers, the longest to about 12 mm long.
Fruit: Small, round, greenish to brown, ca 5 mm in diameter,
dehiscent by a longitudinal slit
Seed: 1.1 mm long, tuberculate, black.
Cultivation: It’s quite prone to rot, especially after the first
flowering. Needs a well-drained soil. Watering should be rather
infrequent, but abundant, so that the soil becomes completely soaked.
The fact that the plant retracts into the soil, and assumes a grey-green
colouring between waterings, is perfectly natural and doesn’t cause any
damage. Keep dry in winter or when night temperatures remain below 10°
C. It is hardy to -4°C for a short period. Assure a good ventilation.
Exposure: Full sun where it obtains a flat natural looking aspect, or