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Accepted Scientific Name: Gymnocalycium castellanosii Backeb.
Kaktus-ABC [Backeb. & Knuth] 287, 416. 1936 [12 Feb 1936] Backeb., F.M.Knuth
Origin and Habitat: Cordoba and La Rioja, Argentina.
Habitat: It is found rocky patches, gravelly slopes, granite or on red sandstone mountains in scarce and almost deprived of nutrients soil, with summer daily temperatures raising above 40° C. The species grows between dense, spiny bushes in chaco forest.
Gymnocalycium castellanosii Backeb.
Kaktus-ABC [Backeb. & Knuth] 287, 416. 1936 [12 Feb 1936]
- Gymnocalycium castellanosii Backeb.
- Gymnocalycium castellanosii subs. acorrugatum (J.G.Lamb.) R.Kiesling & D.Metzing
- Gymnocalycium acorrugatum J.G.Lamb.
- Gymnocalycium ferox (Backeb.) Slaba
Gymnocalycium castellanosii subs. bozsingianum (Schütz) Amerh. & H.Till
Gymnocalycium 19(3): 675. 2006 [Aug 2006]
- Gymnocalycium castellanosii subs. bozsingianum (Schütz) Amerh. & H.Till
Gymnocalycium castellanosii subs. ferocius (Backeb. ex H.Till & Amerh.) G.J.Charles
Cactaceae Syst. Init. 20: 18. 2005 [Nov 2005] (a.k.a.as "ferocior")
- Gymnocalycium castellanosii subs. ferocius (Backeb. ex H.Till & Amerh.) G.J.Charles
Description: Gymnocalycium ferox is a local or morphological form of Gymnocalycium castellanosii that, as the name states, is a robust, ferocious, cactus species characterized by thick spines.
Habit: Solitary, strongly armed cactus.
Stem: Dark green, depressed globose, up to 13 cm in diameter, 6-7 cm tall.
Ribs: Deeply notched, with prominent, chin-like tubercles.
Spines: Subulate, stout, thick and curving, yellowish or amber-coloured with darker tips, becoming grey with age.
Central spine: 1(-2), up to 20 or more mm long.
Radial spines: 7-11, unequal, up to 22 mm or more long.
Flowers: Bell-shaped or funnelform, up to 4,5 cm in diameter, white to very light pink with a pink or reddish throat.
Fruits: Spherical or slightly ovoidal green.
Remarks: The taxonomy of this species is not clear. The description has been invalidated. Gymnocalycium ferox (Backeberg) Slaba nom. inval. (Art. 41. 3b), Kaktusy 20(4): 80, 1984. Based on Gymnocalycium hybopleurum var. ferox Backeberg 1966 nom. inval. Other combinations have been proposed by different authors such as Gymnocalycium hybopleurum v. ferox or Gymnocalycium mostii ssp ferocius. Detlev Metzing cited this taxon as synonymous of Gymnocalycium castellanosii ssp. ferocius.
Subspecies, varieties, forms and cultivars of plants belonging to the Gymnocalycium castellanosii group
- Gymnocalycium castellanosii Backeb.: has heavy spines bent backward, stem dull green or bluish-green with 10-12 ribs. Central spines 0-2, radials 5-7(-8). Distribution: La Rioja, San Juan and Cordoba.
- Gymnocalycium castellanosii subs. bozsingianum (Schütz) Amerh. & H.Till: has grey green epidermis, c. 12 rounded ribs with low tubercles, 5 needle-like radial spines3-20 mm long, 0-1 central spine. Distribution: Chepes Viejo, La Rioja, Argentina.
- Gymnocalycium castellanosii subs. ferocius (Backeb. ex H.Till & Amerh.) G.J.Charles: has dark green stems, ribs deeply notched. Spines stout and thick. Centrals 1(-2), 18-20 mm long, radials 7-11, 6-22 mm long. Distribution: Agua de Ramon, Córdoba.
- Gymnocalycium ferox (Backeb.) Slaba: has ferocious thick spines (same as: Gymnocalycium castellanosii subs. ferocius?). Distribution: Cordoba and La Rioja, Argentina.
Bibliography: Major references and further lectures
1) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
2) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
3) James Cullen, Sabina G. Knees, H. Suzanne Cubey "The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass" Cambridge University Press, 11/Aug/2011
4) Demaio, P., Perea, M. & Trevisson, M. 2013. Gymnocalycium castellanosii. In: IUCN 2013. "IUCN Red List of Threatened Species." Version 2013.2. <www.iucnredlist.org>. Downloaded on 03 January 2014.
Cultivation and Propagation: Gymnocalycium ferox 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.
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