Publication: Kakteenjäger
Description
Gymnocalycium mihanovichii 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 mihanovichii 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 mihanovichii var. stenogonum, was included by Graham Charles within (as a synonym of) Gymnocalycium mihanovichii, 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.
Origin and Habitat
Gymnocalycium mihanovichii var. stenogonum comes from Toro Alarachii in the southern Chaco, Argentina.
Altitude range: 100-150 metres above sea level.
Cultivation and Propagation
Gymnocalycium mihanovichii 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.
Bibliography
Major references and further lectures
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Arthur C. Gibson, Park S. Nobel “The Cactus Primer” Harvard University Press, 1990
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David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. “The New Cactus Lexicon” dh books, 2006