Origin and Habitat: Catamarca, Argentina

• Gymnocalycium curvispinum var. acuticostatum hort.

• Gymnocalycium hybopleurum (K.Schum.) Backeb. in Backeb. & F.M.Knuth
• Echinocactus multiflorus var. hybopleurus K.Schum.
• Gymnocalycium multiflorum var. hybopleurum (K.Schum.) P.Fourn.
• Gymnocalycium ambatoense Piltz
• Gymnocalycium ambatoense subs. plesnikii Halda & Milt
• Gymnocalycium catamarcense subs. acinacispinum H.Till & W.Till
• Gymnocalycium catamarcense subs. schmidianum H.Till & W.Till
• Gymnocalycium curvispinum var. acuticostatum hort.
• Gymnocalycium nigriareolatum Backeb.
• Gymnocalycium nigriareolatum f. carmineum H.Till
• Gymnocalycium nigriareolatum var. densispinum Backeb. ex H.Till
• Gymnocalycium nigriareolatum var. simoi H.Till

Description: Gymnocalycium curvispinus var. acuticostatum is one of the several forms of the very variable Gymnocalycium hybopleurum which form a complex of related taxon. Gymnocalycium curvispinus var. acuticostatum is a cultivated form that distinguish for the strong curved spines and the very prominent acute chinlike protrusions on the ribs, and also for the colourful flowers that are often pink or orangish. It It is still unclear whether this variable complex is one or several species. There is so much variation in spination that most authors choose to lump them together until further studies are done.
Habit: Gymnocalycium hybopleurum is usually solitary in habitat, but occasionally branching basally in cultivation It is characterized by a marked variability in the length and shape of the spines and has received many names.
Stem: Hemispherical to globular in shape up to 15 cm tall and in width dark-green or blue-green
Ribs: About 10-13, acute, with small chinlike protrusions.
Central spine: Absent or one, with darker tip.
Radial spines: 7-8, more or less curved, thick and flattened, interwoven around the body up to to 3 cm long, dull creamy or pinkish coloured, later grey.
Flowers: Short-tubed, ivory white (occasionally pinkish) with a red throat.
Blooming season: Flowers are borne in early summer. It flowers quite readily as a young
seedling.
Fruits: Globose to cylindrical, blue-green

Bibliography: Major references and further lectures
1) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
2) 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
3) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
4) N. L. Britton, J. N. Rose “The Cactaceae. Descriptions and Illustrations of Plants of the Cactus Family.” Volume 4, The Carnegie Institution of Washington, Washington 1923, page. 41
5) Curt Backeberg “Die Cactaceae: Handbuch der Kakteenkunde” Gustav Fischer Verlag, Stuttgart New York 1982–1985

Cultivation and Propagation: Gymnocalycium curvispinus var. acuticostatum (=ambatoense) is a summer grower species that is easy to cultivate.
Growth rate: It is a relatively rapidly growing and easily flowering species that will make clumps given the best conditions.
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 -5 C ° C, or less for short periods).
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: Division, direct sow after last frost. 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! To make a cutting twist off a branch and permit it to dry out a couple of weeks, lay it on the soil and insert the stem end partially into the soil. Try to keep the cutting somewhat upright so that the roots are able to grow downward.