Origin and Habitat: Gymnocalycium denudatum subs. angelaeSN|17492]]SN|17491]], (Gymnocalycium angelaeSN|17491]]SN|17492]]), is a microendemic species found only in the region of Paraje Tres Cerros (San Martin department), central-eastern province of Corrientes, in the northeast of Argentina.
Habitat and ecology: This species grows in rocky slopes of a mountain set just a few metres above the loess plain, which is heavily exploited for livestock farming and rice cultivation. This rocky habitats harbour a rich succulent flora comprising: Frailea schilinzkyanaSN|3634]]SN|3634]] and Cereus uruguayanusSN|6507]]SN|6507]] just to cite some of the more common.

• Gymnocalycium denudatum subs. angelae (Mereg.) Prestlé
• Gymnocalycium angelae Mereg.

• Gymnocalycium denudatum (Link & Otto) Pfeiff. ex Mittler
• Cereus denudatus (Link & Otto) Pfeiff.
• Echinocactus denudatus Link & Otto
• Echinocactus denudatus var. leheideliana F.Haage
• Echinocactus intermedius (Hildm.) Schelle
• Gymnocalycium denudatum var. octogonum (K.Schum.) Y.Itô
• Echinocactus denudatus var. octogonus K.Schum.
• Echinocactus denudatus f. octogonus (K.Schum.) Schelle
• Gymnocalycium intermedium (Hildm.) Y.Itô
• Echinocactus denudatus var. intermedius Hildm.
• Echinocactus intermedium (Hildm.) K.Schum.
• Gymnocalycium denudatum var. intermedium auct.
• Gymnocalycium megalothelon (Sencke ex K.Schum.) Britton & Rose
• Echinocactus megalothelos Sencke

• Gymnocalycium denudatum subs. angelae (Mereg.) Prestlé
• Gymnocalycium angelae Mereg.

• Gymnocalycium denudatum var. flavispinum (Mundt in Schelle) Y.Itô
• Echinocactus denudatus var. flavispinus (Mundt in Schelle) Y.Itô

• Gymnocalycium denudatum cv. Jan Suba hort.
• Gymnocalycium denudatum var. subai

Description: Gymnocalycium denudatum subs. angelaeSN|17492]]SN|17491]] (firstly described as Gymnocalycium angelaeSN|7888]]SN|17492]] by Massimo Meregalli in the German Society's journal, Kakteen und andere Sukkulenten in 1998) is a local or morphological form of Gymnocalycium denudatumSN|15257]]SN|7888]], but recognised by some authorities as a legitimate species in its own right. It is separated from Gymnocalycium denudatumSN|7888]]SN|7888]] by hundreds of kilometres. It distinguishes for having smaller flowers with red throat and for a more opaque and pale green colour of the stem.
Taxonomic note: Meregalli, basing on chromosome analysis, concluded that G. angelae was more related to Gymnocalycium mesopotamicumSN|7888]]SN|15257]] than to Gymnocalycium denudatumSN|17492]]SN|7888]].
Habit: Gymnocalycium angelaeSN|17491]]SN|17492]] is a flattened globose cactus species usually solitary with bright green bodies.
Derivation of specific name: The specific epithet honours Mrs. Angeles Gracilea Lopez, the wife of Argentinian botanist Roberto Kiesling.
Stems: Flattened-hemispheric, surface smooth, shiny bright to midgreen, to 8 cm tall and 10 cm across.
Roots: It has two to three main fibrous roots
Ribs: Seven to ten, flat, wide, bluntly rounded, grooved transversely. Tubercles very few per ribs, inconspicuous.
Areoles: Oval with whitish wool.
Central spines: Absent.
Radial spines: 7 thin and curved, adpressed on the surface, yellowish, becoming grey with darker bases as they age 1.5-2 cm long long.
Flowers: Near the top of the stem, wide funnel-shaped, petals white, pink inside at the base of the flower tube c. 4 cm long and 5 cm in diameter at anthesis.
Fruits: Green, elongated at maturity, up to 3 cm long.
Seeds: 1.9-2 mm long, 2-2.1 mm wide and 1.2 mm thick in the centre. Testa shiny, reddish brown.
Chromosome number: 2n = 22

Bibliography: Major references and further lectures
1) Eggli, Urs; Newton, Leonard E. “Etymological Dictionary of Succulent Plant Names”. Springer. 2004
2) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
3) Gymnocalycium angelae in: Kakteen und andere Sukkulenten. 49(12), 283–290, 1998.
4) Wikipedia, "Gymnocalycium angelae -Wikipedia, Die freie Enzyklopädie", 2014,
<https://de.wikipedia.org/w/index.php?title=Gymnocalycium_angelae&oldid=128477688
Online; Stand 5. April 2016
5) Meregalli, Massimo «Gymnocalycium angelae spec. nov., eine neue Art aus Argentinien». Kakteen und andere Sukkulenten 49 (12): 283-290. 1998
6) Graham, C. “Gymnocalycium in habitat and culture.” Stamford 2009
7) Colaboradores de Wikipedia. Gymnocalycium angelae [en línea]. Wikipedia, La enciclopedia libre, 2016 [fecha de consulta: 5 de abril del 2016]. Disponible en <https://es.wikipedia.org/w/index.php?title=Gymnocalycium_angelae&oldid=89079953>.

Cultivation and Propagation: Gymnocalycium angelaeSN|17492]]SN|17492]] is a summer grower species that is easy to cultivate. It requires partial shade with warm temperatures (even in winter), and frequent moisture, without a dry period.
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), reduce waterings in winter at a minimum temperature of 5°C (but not deep completely dry for long time).
Fertilization: Feed with a high potassium fertilizer in summer.
Hardiness: Reputedly resistant to light frost if kept on the dry side prior to, and during, cold weather, but for safe cultivation it is best to avoid freezing temperatures (5-10° C minimum temperature in winter are optimal).
Exposition: The plant tolerates 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: 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!