Origin and Habitat: Salta, Argentina
Altitude: 3000-3600m

• Gymnocalycium spegazzinii var. horizonthalonium Backeb.
• Gymnocalycium horizonthalonium Frič ex Kreuz.

• Gymnocalycium spegazzinii Britton & Rose
• Echinocactus loricatus Speg.
• Gymnocalycium loricatum Speg.
• Gymnocalycium spegazzinii subs. armatum (F.Ritter) Halda & Šorma
• Gymnocalycium armatum F.Ritter
• Gymnocalycium cardenasianum f. armatum (F.Ritter) H.Till & Amerh.
• Gymnocalycium spegazzinii var. armatum (F.Ritter) Slaba & Šorma
• Gymnocalycium spegazzinii subs. fiambalense
• Gymnocalycium spegazzinii var. horizonthalonium Backeb.
• Gymnocalycium horizonthalonium Frič ex Kreuz.
• Gymnocalycium spegazzinii var. major Backeb.
• Gymnocalycium spegazzinii var. punillense H.Till & W.Till
• Gymnocalycium spegazzinii var. recii Milt
• Gymnocalycium spegazzinii subs. sarkae Halda & Milt
• Gymnocalycium spegazzinii var. unguispinum Slaba

• Gymnocalycium spegazzinii subs. cardenasianum (F.Ritter) R.Kiesling & D.Metzing
• Gymnocalycium cardenasianum F.Ritter

• Gymnocalycium cardenasianum cv. Japanese Selection

Description: Gymnocalycium spegazzinii var. horizonthaloniumSN|996]]SN|15249]] is a former synonym of Gymnocalycium spegazziniiSN|996]]SN|996]] which is characterized by a variability in the length and shape of the spines and has received many names. It is really difficult to tell var. horizonthalonium apart from the standard species and most authors choose to lump them together. It is not difficult to see how a naming error could have arisen here, leading to confusion with the not entirely dissimilar Echinocactus horizonthaloniusSN|1711]]SN|1711]].
Habit: Gymnocalycium spegazziniiSN|15249]]SN|996]] is a geophyte cactus usually solitary and barely rising above ground level with a swollen root system.
Stem: Noticeably flatten, in nature it is partially underground, greyish-green, brownish-grey to almost black up to 18 cm (or more) in diameter, 6 cm tall (up to 10 cm tall in cultivation). Apex depressed an woolly. Will not offset.
Ribs: 10-33 (usually about 13-15) broad an low, evenly subdivided in confluent rounded tubercle, not chinned. Transversal grooves rudimentary or absent.
Areoles: Elongate 8-10 x 4-6 mm yellowish or greyish.
Central spine: Absent.
Radial spines: 5-7(-9) strong, subulate, +/- flattened, 25-55 mm long, typically recurved, and add-pressed against the body and most attractive, the young spines are yellowish or blackish and become brownish-grey as they ages.
Flowers: Infundibuliform on the plant apex 70 mm long, 50 mm in diameter. Outer tepals spatulated whitish or pinkish with a glaucous green midrib. Inner tepals smaller, lanceolated white with a pink midrib and basally crimson coloured (red throated). Filament crimson or violet, anthers pale-yellow, style white to violet-pink, stigma with 10-16 white to rose-coloured lobes. Scales on the ovary few and broad.
Blooming season: Flowers are produced in late spring and remain open for up to twelve days.
Fruits: Elongate up to 35 mm long, green covered with bluish pruine.
Seeds: Of the microsemineum type +/- 0.9 mm.

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
5) Curt Backeberg “Die Cactaceae: Handbuch der Kakteenkunde” Gustav Fischer Verlag, Stuttgart New York 1982–1985
6) John Borg “Cacti: a gardener's handbook for their identification and cultivation” Blandford P., 1970
7) The National Cactus and Succulent Journal: The Official Journal of the National Cactus & Succulent Society, Volumes 35-37 - Page 111, 1980

Cultivation and Propagation: Gymnocalycium spegazziniiSN|996]]SN|996]] is a summer grower species that is easy to cultivate.
Growth rate: It is a slow 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: 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.