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Origin and Habitat: Gymnocalycium alboareolatum is known from only one population with an extent of occurrence of less than 100 km2 in La Rioja (area around Villa Bustos), Argentina. The species is locally abundant but there is a continuing decline of mature individuals.
Altitude range: 800-1,100 (-1,500?) metres above sea level.
Habitat and ecology: The species occurs in monte shrubland. It usually occurs buried in the ground making it very difficult to see when not in flower or fruit. It grows in gravelly slope. The major threat for the species is urban development, the only known populations grows at the edge of a town that is expanding. Parts of the population have been affected by urbanization already and this will not cease in the near future. Hence the species is listed as Critically Endangered. The species is not known to be used or traded.
- Gymnocalycium albiareolatum Rausch
Gymnocalycium albiareolatum Rausch
Succulenta (Netherlands) 64: 213, fig. 1985 [ as 'albiareolatum' ]
- Gymnocalycium albiareolatum Rausch
- Gymnocalycium alboareolatum var. ramosum Rausch
UKRAINIAN (Українська): Гімнокаліціум альбіареолатум, Гімнокаліціум білоареоловий
Description: Gymnocalycium albiareolatum is a beautiful species, of modest size, particularly attractive for its beautiful solitary, gray-green, flattened stems less than 6 cm in diameter with very prominent white areoles. The flowers are silvery white often pink flushed usually in clusters from June to September.
Note: Gymnocalycium albiareolatum was published by Rausch, in Succulenta 64(10): 213-214, 1985. The name was published with the spelling "alboareolatum”. Since this name is grammatically incorrect, it has been corrected into "albiareolatum" according to Art. 60.8 and Ree. 60G.
Derivation of specific name: The species name means 'white areoles' from Latin 'albus', white and Latin 'areola', areole.
Stem: Solitary or clumping ( "var ramosum" ), spherical-flattened, to 6(-10) cm in diameter, grey-green, glaucous (brownish in the dry season), barely rising above ground level with a swollen underground root system.
Ribs: (8-)9-11(-13), straight with well-defined chinlike protrusions to up to 1 cm in height below the areoles.
Areoles: Quite large, initially with a thick, white wool, round to oval, up to 5 mm thick.
Central spines: Absent.
Radial spines: 6-7, bent, curving back toward the body, hard, brown, 1 cm in length.
Flowers: Funnel-shaped, slender, silver-white on the outside, pink inside (with reddish throat), outer perianth segments with a green stripe to 6.5 cm long and 4.5 cm in diameter (rarely to 6cm).
Fruits: Oval, to club shaped, blue-green, glaucous, 25-35 mm long and up to 1 cm in diameter.
Seeds: Dull black, hat-shaped and about 1mm in diameter.
Rlated species: Gymnocalycium hossei is probably the closest relative of Gymnocalycium albiareolatum. A quite similar-looking form of Gymnocalycium kieslingii (Gymnocalycium kieslingii f. albiareolatum) growing in the same area (though usually at about 1500 m altitude) has been often indicated as a synonym of Gymnocalycium albiareolatum, but has different seeds and belongs to another group.
Subspecies, varieties, forms and cultivars of plants belonging to the Gymnocalycium albiareolatum group
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) Gymnocalycium albiareolatum in: Allionia: bollettino dell'Istituto ed orto botanico dell'Università di Torino, Arti Grafiche P. Conti, 1995
5) Demaio, P., Trevisson, M. & Perea, M. 2013. Gymnocalycium albiareolatum. The IUCN Red List of Threatened Species 2013: e.T152872A688953. http://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T152872A688953.en. Downloaded on 07 February 2016.
6) Pilbeam, John. “Gymnocalycium: A Collector's Guide.” A. A. BALKEMA / ROTTERDAM / BROOKFIELD / 1995
7) Preston-Mafham Rod Preston-Mafham Ken “Cacti: The Illustrated Dictionary” 1995
8) Véro + Chris Kettinger “Gymnocalycium albiareolatum (Rausch 1985)” Retrieved 06 February 2016 from <http://www.kuas-kettinger.de/gymnocalycium_albiareolatum.html>
9) “Gymnocalycium alboareolatum” in: Gymnocalycium org, Retrieved 06 February 2016 from <http://www.gymnocalycium.org/gatunki/alboareolatum.html>
Cultivation and Propagation: Gymnocalycium albiareolatum is a summer grower species that is easy to cultivate.
Growth rate: It is a relatively slowly growing but 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: 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: 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!
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