Accepted Scientific Name: Gymnocalycium mihanovichii var. stenogonum
Kakt Listy 16(10): 109-159
Gymnocalycium stenogonum (Gymnocalycium mihanovichii var. stenogonum) Photo by: Valentino Vallicelli
Origin and Habitat: Gymnocalycium mihanovichiiSN|11929]]SN|11929]] var. stenogonum comes from Toro Alarachii in the southern Chaco, Argentina.
Altitude range: 100-150 metres above sea level.
Synonyms:
See all synonyms of Gymnocalycium mihanovichii
Description: Gymnocalycium mihanovichiiSN|11929]]SN|11929]] var. stenogonum is a globular rugged looking plant with well-developed ribs found by Fric in 1926 and described by him and Pazout in 1948. It is a local or morphological form of Gymnocalycium mihanovichiiSN|11929]]SN|11929]] distinguished from the type by its somewhat larger stem, up to 15 cm in diameter, smooth fresh green to bronze in full sun and unusual greenish flowers. Gymnocalycium mihanovichiiSN|11929]]SN|11929]] var. stenogonum, was included by Graham Charles within (as a synonym of) Gymnocalycium mihanovichiiSN|11929]]SN|11929]], suggesting that there is not really a fundamental difference between the two.
Stems: Up to 5 cm in diameter, fresh green to bronze with a dull violet shimmer (depending on exposure).
Ribs: 8 (in older subjects), acute, with pronounced horizontal stripes. Each rib has a bump or a "chin" between successive areoles, and the position of of the fruit shows where the flower is formed on the upper side of the areole just below the chin.
Spines: c.5, up to 2 cm long. We see that this description can be applied to all the synonyms of the type species taxa.
Subspecies, varieties, forms and cultivars of plants belonging to the Gymnocalycium mihanovichii/stenopleurum group
The name Gymnocalycium mihanovichii v. friedrichii was introduced by Werdermann in 1936. Pazout suggested the name G. friedrichii nom. inval. in 1964 but it has not been officially approved. In 1979 Ritter made a description of Gymnocalycium stenopleurum that sometimes can be found under the incorrect name G. mihanovichii v. stenopleurum n. n. (don't confuse it with v. stenogonum). Thus we have 3 taxa: "mihanovichii", "friedrichii" and "stenopleurum". Not taking into account their taxonomic definition they are basic points of the complex with many transitional forms between. These three taxa spread from south to north (North-Western Paraguay): The typical "mihanovichii" inhabits the very south of the area – south and south-east of province Boqueron; "stenopleurum" inhabits a limited area on the very north – in Cerro Leon region and has characteristic recognizable habitus; for "friedrichii" all the area between two mentioned points is indicated.
- Gymnocalycium friedrichii (Werderm.) Pazout: Distingushed from Gymnocalycium miahanovichii for the prevalently purplish pink, wide open flowers and well-pronounced polymorphism of spines. Besides it has tall slender ribs and roller-shaped prominent thickening around areoles.
- Gymnocalycium friedrichii f. cristatum hort.: Crested form with nice stems reddish brown to dark grape coloured.
- Gymnocalycium friedrichii var. moserianum Pazout ex Moser: has brown bodies 2 times larger than G. friedrichii, with sharp ribs striped with white, and only 3 weak spines. Flowers are pale pink and open up entirely. Distribution: Yrebdaque, Boquerón, Paraguay.
- Gymnocalycium mihanovichii (Frič ex Gürke) Britton & Rose: It has wider, lower ribs, in juvenile plants divided into separate chins, in maturity every rib have flat surface and a pleat above each areole. But the essential thing is its pale or brownish-yellow, not fully opening flower.
- Gymnocalycium mihanovichii var. filadelfiense Backeb.
- Gymnocalycium mihanovichii var. stenogonum Frič & Pazout: has larger stem (up to 15 cm in diameter), smooth fresh green to bronze in full sun. The greenish flowers are also larger. Distribution: Toro Alarachii, southern Chaco, Argentina.
- Gymnocalycium mihanovichii cv. Hibotan hort.: chlorophylles mutants, characterized by more or less red coloured bodies.
- Gymnocalycium mihanovichii cv. Hibotan f. cristata hort.: this is the crested form of the chlorophyll-less cv. Hibotan characterized by more or less red coloured bodies.
- Gymnocalycium mihanovichii cv. Nishikii hort.: variegated cultivars only partially de-coloured.
- Gymnocalycium stenopleurum F.Ritter: Distingushed from Gymnocalycium miahanovichii for the white, fully opening flowers. Distribution: Cerro León, Boquerón department of Paraguay.
Bibliography: Major references and further lectures
1) Arthur C. Gibson, Park S. Nobel “The Cactus Primer” Harvard University Press, 1990
2) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
Cultivation and Propagation: Gymnocalycium mihanovichiiSN|11929]]SN|11929]] var. stenogonum is a summer grower species that is easy to cultivate.
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), keep dry in winter at a minimum temperature of 0°C.
Fertilization: Feed with a high potassium fertilizer in summer.
Hardiness: Quite frost resistant if kept dry -5° C (Temperature Zone USDA 9-10), 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: Seeds (seldom produces offsets). 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! Colour mutants and variegates cultivars are propagated by graft.