Origin and Habitat: South-east of Bolivia ( Cochabamba, Santa Cruz, Chuquisaca, Potosi)
Altitude: It can be found at elevations of 1000-2500 metres above sea level.
Habitat: Grows often semi-buried in in deep rich sandy soil, rather in sunny rocky areas, on slopes or under spiny shrubs, at the border and clearings of the dry Chaco forest. It has a wide range, is abundant and the threats that affect part of its range are minor. Subsistence farming, agriculture and goat grazing are minor threats to the species in parts of its wide range.

• Gymnocalycium pflanzii subs. zegarrae (Cárdenas) G.J.Charles
• Gymnocalycium pflanzii var. zegarrae (Cárdenas) Donald
• Gymnocalycium zegarrae Cárdenas

• Gymnocalycium pflanzii (Vaupel) Werderm.
• Echinocactus pflanzii Vaupel
• Gymnocalycium comarapense Backeb.
• Gymnocalycium lagunillasense var. karmiri Kníže in Pilbeam
• Gymnocalycium marquezii Cárdenas
• Gymnocalycium marquezii var. angostura hort.
• Gymnocalycium marquezii var. formesense hort.
• Gymnocalycium marquezii var. pilcomayo hort.
• Gymnocalycium pflanzii var. albipulpa F.Ritter
• Gymnocalycium pflanzii subs. argentinense H.Till & W.Till
• Gymnocalycium marquezii var. argentinense Backeb.
• Gymnocalycium pflanzii f. chuquisacanum (Cárdenas) Donald
• Gymnocalycium chuquisacanum Cárdenas
• Gymnocalycium pflanzii var. izozogsii (Cárdenas) Donald
• Gymnocalycium izozogsii Cárdenas
• Gymnocalycium pflanzii var. lagunillasense (Cárdenas) Donald
• Gymnocalycium lagunillasense Cárdenas
• Gymnocalycium pflanzii var. millaresii (Cárdenas) Donald
• Gymnocalycium millaresii Cárdenas
• Gymnocalycium zegarrae subs. millaresii (Cárdenas) H.Till & W.Till
• Gymnocalycium pflanzii var. riograndense (Cárdenas) Donald
• Gymnocalycium riograndense Cárdenas
• Gymnocalycium zegarrae subs. riograndense (Cárdenas) H.Till & Amerh.
• Gymnocalycium zegarrae var. riograndense (Cárdenas) H.Till & Amerh.
• Gymnocalycium zegarrae var. coquimbana hort.
• Gymnocalycium zegarrae var. saipinense hort., Kníže

• Gymnocalycium pflanzii subs. zegarrae (Cárdenas) G.J.Charles
• Gymnocalycium pflanzii var. zegarrae (Cárdenas) Donald
• Gymnocalycium zegarrae Cárdenas

Description: Gymnocalycium pflanzii subs. zegarraeSN|18750]]SN|18764]] (better-known in cultivation as G. zegarrae) is a naturally occurring larger variant of Gymnocalycium pflanziiSN|18764]]SN|18750]] that looks very much like the standard pflanzii but fruits are green or rarely orange with white pulp (in subsp. pflanzii fruits are deep red-carmine at maturity and have a cherry-red pulp). However the two plants are quite similar and it is hard to tell apart one from the others if not fruiting.
Habit: It is a solitary or slowly clustering cactus, with peculiar spine clusters characteristically bent backward in a distinctive fashion.
Stem: Flattened-globose, 11-18 (at times up to 30 cm) cm in diameter, 6-10(-25) cm tall grey-green, to olive green. The epidermis has a velvety appearance. The apex is slightly depressed and woolly.
Ribs: 13 to 22 thick, large, divided into indistinct, polygonal-rounded (not chinned) tubercles, separated by arched furrows.
Roots: Fibrous
Areoles: Large long, oval up to10 mm long, with light grey felt, then blackish with time.
Spines: Strong, very stiff, bent backward, initially blackish with a brown base then becoming grey-pinkish to whitish brown with black point.
Radial spines: About 8, rigid slightly curved, radiating laterally, somwhat pectinated, up to 25 mm long.
Central spines:One, subulate, rigid 25-30 mm (rarely up to 5 cm).
Flowers: Campanulate to cup-shaped born near the apex, diameter and height 30-45 mm. Pericarpell dull green very short.
Fruits: Globose to ovoid of approximately 2 cm of diameter, green or rarely orange with white pulp and splitting open vertically at maturity.
Seeds: Microsemineum type, section pirisemineum, very smal.

Bibliography: Major references and further lectures
1) Kakteen und andere Sukkulenten . 9(2): 21–22 1958
2) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
3) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
4) James Cullen, Sabina G. Knees, H. Suzanne Cubey "The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass" Cambridge University Press, 11/Aug/2011
5) Friedrich Ritter “Kakteen in Südamerika: Ergebnisse meiner 20jährigen Feldforschungen” volume 2, 1980
6) Demaio, P., Lowry, M., Ortega-Baes, P., Perea, M. & Trevisson, M. 2013. Gymnocalycium pflanzii. In: IUCN 2013. "IUCN Red List of Threatened Species." Version 2013.2. <www.iucnredlist.org>. Downloaded on 17 February 2014.

Cultivation and Propagation: Gymnocalycium are very gratifying plants, their culture is easy and their flowering is abundant if we give them a well drained relatively rich substrate (if possible not limestone).
Growth rate: It is a relatively rapidly growing and easily flowering species.
Soils: It likes very porous standard cactus mix soil. Prefer a low pH compost, avoid substrata rich in limestone; otherwise growth will stop altogether.
Repotting: This plant needs plenty of space for its roots, repotting should be done every other year or when the it has outgrown its pot. Use pot with good drainage.
Watering: Needs moderate to copious waterings in summer, but do not overwater (Rot prone), keep dry in winter at a minimum temperature of 0°C.
Fertilization: Feed with a high potassium fertilizer in summer.
Hardiness: Reputedly resistant to frost if kept on the dry side prior to, and during, cold weather (hardy to -12 C ° C, or less for short periods), but for safe cultivation it is best to avoid freezing temperatures.
Exposition: The plant tolerates extremely bright situations but enjoys filtered sunlight or afternoon shade, inside it needs bright light, and some direct sun. Tends to bronze in strong light, which encourages flowering and heavy spine production, but is likely to suffer from sun scorch or stunted growth if over exposed to direct sunlight during the hottest part of the day in summer.
Uses: It is an excellent plant for container growing. It always looks good and stays small. It look fine in a cold greenhouse and frame or outdoor in a rockery.
Pests & diseases: It may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for:
- Red spiders: Red spiders may be effectively rubbed up by watering the plants from above.
- Mealy bugs: Mealy bugs occasionally develop aerial into the new growth among the wool with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects.
- Scales: Scales are rarely a problem.
- Rot: This species is particularly easy and accommodating, seldom suffer of cryptogamic diseases. Rot it is only a minor problem with gymnocalyciums if the plants are watered and “aired” correctly. If they are not, fungicides won't help all that much.
Propagation: Usually by Seeds.. Seeds germinate in 7-14 days at 21-27° C in spring, remove gradually the glass cover as soon the plants will be well rooted (ca 1-2 weeks) and keep ventilated, no full sun for young plants! The grafting is useless (excluded the cultivars deprived of chlorophyll), it does not bring anything concrete.