Origin and Habitat: Sierra de Ambato; province of Catamarca, Argentina.
Altitude range. 1000-3500 metres above sea level.
Habitat and ecology: Gymnocalycium tillianumSN|28336]]SN|28337]] grows among rocks on steep, grassy slopes , and in fairly dense dry scrubby woodland. The closely related Gymnocalycium carminanthumSN|28337]]SN|28336]], grows in the same area, and differs mainly by the rather particular type of seed.

• Gymnocalycium tillianum Rausch

• Gymnocalycium oenanthemum Backeb.
• Gymnocalycium oenanthemum subs. carminanthum (Borth & Koop) H.Till
• Gymnocalycium carminanthum Borth & Koop
• Gymnocalycium tillianum Rausch
• Gymnocalycium tillianum subs. montanum (Slaba) F.Berger
• Gymnocalycium carminanthum var. montanum Slaba

Description: Gymnocalycium tillianumSN|28334]]SN|28337]] is a short, squat Argentinian cactus, with shining green stems that grow 10 cm tall and 15 cm wide. It has long, black-brown, curving spines and relatively large pale pink, carmine red or wine-red flowers in spring that stand out. The richness of the red always provides an inner glow of satisfaction. Spherical fruit follow in summer. Gymnocalycium tillianumSN|28337]]SN|28337]] is almost identical to the standard Gymnocalycium oenanthemumSN|28337]]SN|28334]] and it is hard to tell apart one from the others, if not for the geographical provenance and a few little differences in seeds morphology and they are not considered distinct.
Stem: Solitary, flattened globose, leaf-green, grey-green or bluish-green; up to 12-15 cm in diameter, and 8-10 cm tall. Apex depressed, woolly, covered by the spines from neighbouring areoles.
Roots: Fibrous.
Ribs: 11 to 13 (12 to 18 according to Ritter), sinuous, acute or somewhat rounded, separated by deep vertical furrows. Tubercles rounded, with prominent chins separates by straight transverse furrows, occupying the whole width of the ribs.
Areoles: Oblong, 8 × 5 mm, initially yellow then white.
Radial spines: 5 (3 to 8, Ritter), stout, stiff, erect, , straight to slightly curved, 25-30 mm long one pointing downward, others in pairs curving sideways. .
Central spines: absent (occasionally one is present, similar to the radial, Ritter), erect and slightly bent upwards. Young spines translucent, grey-brown with dark tip to blackish, becoming grey with brownish points.
Flowers: Apical, 30-35 mm long, 25-35(-40) mm in diameter. Pericarpel short (15 mm), green, with rounded olive-green scales, initially edged with white and a pink point, then bordered with pink. Outer perianth segments spatulate, cherry-red with an olive-green wide median band. Inner perianth segments spatulate, but narrower, with a small mucro, carmine red. Throat carmine. Filaments carmine pink. Anthers light yellow. Style carmine to orange-red. Stigma white to yellowish, with 9-11 lobes, under the stamens.
Fruits: Flattened globose to spherical, light green to brownish green with lighter scales.
Seeds: ca. 1 mm. Testa matt blackish-brown, finely granulous. Hilum large basal, circled with a strong prominent white ring.

Bibliography: Major references and further lectures
1) J.G. Lambert “Cacti of Argentina” 2nd edition Revised and supplemented 1997 <https://www.cactuspro.com/biblio_fichiers/pdf/Lambert/LambertEN.pdf>
2) “Botanica: The Illustrated A-Z of Over 10,000 Garden Plants and how to Cultivate Them” Mynah, 1997
3) John Pilbeam “Cacti for the Connoisseur: A Guide for Growers & Collectors” Timber Press, 01 Jule 1987
4) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001

Cultivation and Propagation: Gymnocalycium tillianumSN|28337]]SN|28337]] is a summer grower species that is easy to cultivate.
Growth rate: It is a relatively slowly growing but 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 -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. In full sun turns an uneven brownish red colour.
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: 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!