Gymnocalycium occultum P131 Tres Puentes, Catamarca, Argentina 700m
This is one the most unusual and desirable of the Gymnocalyciums.
 

Description: G. occultum (= G. stellatum)  is a beautiful, slowly-growing plant with a noticeably flatten body,  at first solitary, later clustering.
Stem: Dark grayish-brown to olive-coloured epidermis, flattened globose, 7.5-10 cm in diameter.   It will offset after a considerable period of time.
Ribs: 7-11, flat, round, without prominent chin-like protrusions.
Spines: 3-5, dark brown, becoming grey with age, spider-like, add-pressed, short, straight to slightly curved and flattened against the stem (rarely sticking out - easy cactus to handle)
Flowers: Creamy-white with a dull red throat, up to 6,5 cm. long, 4.5 cm. in diameter.
Fruit: Cylindrical.
Blooming season: Flowers are produced in late spring and remain open for up to twelve days.

Two subspecies are recognized:
The “occultum” subspecies occurs in Catamarca.
The “stellatum” subspecies occurs in Cordoba.

Scientific name:  Gymnocalycium occultum Fric ex Schütz 1962

Origin:  Argentina Catamarca at low elevation.

Conservation status: Listed in CITES appendix 2.

• Gymnocalycium stellatum subsp. occultum (Frič ex Schütz) H.Till & W.Till, 1996
• Gymnocalycium obductum Piltz,
  Pubblished in: Succulenta 69(4): 74-78 + title plate, 1990 = stellatum
• Gymnocalycium stellatum (Speg.) Speg. 1925
• Echinocactus stellatus Spegazzini
• Gymnocalycium asterias Y-Ito
• Gymnocalycium asterium A. castellanos 1957 (Illegitimate name)
• Gymnocalycium stellatum ssp. asterium

Cultivation: This Gymnocalycium is supposed to be one of the most difficult species in cultivation, and very slow to get to a reasonable size. It will offset after a considerable period of time.   It is a summer-growing species that needs regular water in summer (but do not over-water).  Keep rather dry in winter.  This plant does not like extremely bright situations.  Give it some shade during the hottest part of the day.  Keep this plant in a low PH compost;  otherwise growth will stop altogether.  Feed it with a high potassium fertilizer in summer.  It is quite frost resistant if kept dry (hardy to  -5° C)

Propagation: Direct sow after last frost.(seldom produces offsets)

Photo of conspecific taxa, varieties, forms and cultivars of plants belonging to the Gymnocalicyum stellatum complex

• Gymnocalycium stellatum  ( G. asterias)
• Gymnocalycium occultum ( G. stellatum spp. occultum)
• Gymnocalycium ragonesii
• Gymnocalycium ragonesii forma cristata