Origin and Habitat: Argentina Northwest (San Luis).
Altitude range: It can be found at elevations around 900 metres above sea level.
Type locality: Argentina, San Luis province, near Juan Llerena, m 900.

• Gymnocalycium monvillei f. villamercedense H.Till & Neuhuber
• Gymnocalycium achirasense var. villamercedense (H.Till & Neuhuber) V.Gapon
• Gymnocalycium villamercedense F.Ritter

• Gymnocalycium monvillei (Lem.) Britton & Rose
• Echinocactus monvillei Lem.
• Gymnocalycium monvillei var. coloratum Neuhuber
• Gymnocalycium monvillei var. confusa Neuhuber
• Gymnocalycium monvillei subs. gertrudae (Neuhuber) Neuhuber
• Gymnocalycium monvillei var. gertrudae Neuhuber
• Gymnocalycium monvillei var. orientale Neuhuber
• Gymnocalycium achirasense var. orientale (Neuhuber) V.Gapon
• Gymnocalycium monvillei subs. achirasense var. orientale Neuhuber in H.Till & Neuhuber
• Gymnocalycium monvillei var. safronovii V.Gapon
• Gymnocalycium monvillei var. steineri H.Till
• Gymnocalycium multiflorum f. steineri.
• Gymnocalycium multiflorum (Hook.) Britton & Rose
• Echinocactus multiflorus Hook.
• Gymnocalycium multiflorum var. parisiense (K.Schum.) P.Fourn.
• Echinocactus multiflorus var. parisiensis K.Schum.
• Echinocactus multiflorus f. parisiensis (K.Schum.) Schelle
• Gymnocalycium polyanthum var. parisiense (K.Schum.) Y.Itô
• Gymnocalycium ourselianum (Cels ex Salm-Dyck) Y.Itô
• Echinocactus ourselianus Monv., Cels ex Salm-Dyck
• Gymnocalycium multiflorum var. ourselianum (Cels ex Salm-Dyck) H.Till & W.Till

• Gymnocalycium monvillei subs. achirasense (H.Till & Schatzl) H.Till
• Gymnocalycium achirasense H.Till & Schatzl
• Gymnocalycium horridispinum subs. achirasense (H.Till & Schatzl) G.J.Charles
• Gymnocalycium horridispinum var. achirasense (H.Till & Schatzl) Lodé
• Gymnocalycium monvillei var. chacrasense Neuhuber
• Gymnocalycium achirasense var. chacrasense (Neuhuber) V.Gapon
• Gymnocalycium monvillei subs. achirasense var. chacrasense
• Gymnocalycium monvillei var. echinatum Neuhuber
• Gymnocalycium achirasense subs. echinatum (Neuhuber) V.Gapon
• Gymnocalycium monvillei var. kainradliae Neuhuber
• Gymnocalycium achirasense subs. kainradliae (Neuhuber) V.Gapon
• Gymnocalycium monvillei f. villamercedense H.Till & Neuhuber
• Gymnocalycium achirasense var. villamercedense (H.Till & Neuhuber) V.Gapon
• Gymnocalycium villamercedense F.Ritter

• Gymnocalycium monvillei subs. brachyanthum (Gürke) H.Till
• Echinocactus brachyanthus Gürke
• Gymnocalycium brachyanthum (Gürke) Britton & Rose

• Gymnocalycium monvillei subs. horridispinum (G.Frank ex H.Till) H.Till
• Gymnocalycium horridispinum G.Frank ex H.Till

Description: Gymnocalycium monvilleiSN|31132]]SN|11438]] f. villamercedense (Basionym: Gymnocalycium villamercedenseSN|11434]]SN|31132]] Ritter ) is a local or morphological form of the widespread Gymnocalycium monvillei subs. achirasenseSN|31132]]SN|11434]]. This taxa is one of the first Ritter´s findings recorded with his field number FR 6, seeds has been sold by his sister Hildegard Winter in Germany under the name Gymn. multiflorum at first. The name Gymnocalycium villamercedenseSN|11438]]SN|31132]] was mentioned only later. It is a globular cactus usually solitary without a swollen taproot system. The most remarkable trait of this taxon is the very developed chin-shaped protuberances which can appear like “beaks” under the areoles. Unlike the other taxa of subsp. achirasense that have brown-green, yellowish-brown or yellow fruits the villamercedense has red fruits.
Stem: About 9-12 cm thick and high, green.
Ribs: 13 to 18 divided into strong chinlike tubercles.
Areoles: 7-10 mm long, about 5 mm apart.
Radial spines: About 10, yellowish, not red or black, 1-2 cm long.
Central spines: 1-4, 20-25 mm long, curved upwards.
Fruits: Round, red.
Seeds: Small, black or reddish, slightly tuberculate, hilum often concave, white, long and narrow.

Bibliography: Major references and further lectures
1) “Gymnocalycium achirasense Till & Schatzl” Kakteen und andere Sukkulenten 38 191, 1987

Cultivation and Propagation: Gymnocalycium monvilleiSN|11438]]SN|11438]] f. villamercedense (=achirasense) 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.