Publication: Cact. Hort. Dyck. (1849) 87. 1850
Description
Mammillaria formosa subs. microthele is a low-growing flattened plants, clumping with tight, short white spines which forms low, many-headed, mounds in time. Some authors consider Mammillaria formosa subs. microthele to be sufficiently distinct to deserve its own formal status: Mammillaria microthele.
Stems: Almost discoidal to globose, apically depressed, dividing dichotomously, each stem are up to 6 cm in diameter.
Tubercles: About 6 mm long, naked or woolly in their axils.
Radial spines: 22-24 tiny, white-setiform, spreading, 2 to 4 mm long that almost obscure the stem.
Central spines: 2, much stouter than the radials, 2 mm long or less.
Flowers: Small (3-5 mm) long in a ring around the sides of the stem, nearly pure white to flesh-coloured without, white within.
Blooming season: Flowers are produced in spring over a several weeks period.
Fruits: Clavate, 10 (or more) mm long.
Seeds: Rather large, black.
Remarks: The so called “superfina” is a particular nice selected form with even more small tubercles and spines.
Origin and Habitat
Mexico (Coahuila, San Luis Potosi, Tamaulipas).
Altitude: 1000-2200 metres above sea level.
Habitat: It is usually found in limestone slopes, hills and plains in xerophytic shrubland. It is a very common to abundant species that grows along with a rich succulent flora such as: Turbinicarpus jauernigii, Leuchtenbergia principis, Thelocactus tulensis, Echinocereus diguetii, Escobaria zilziana, Mammillaria surculosa, Neolloydia conoidea, Echinocereus pentalophus, Opuntia microdasys, Ferocactus latispinus, Coryphantha erecta, Glandulicactus crassihamtaus often among shrubs of Agave lechuguilla and Hechtia glomerata.
Cultivation and Propagation
Mammillaria formosa subs. microthele is a slow growing species.
Soil: Use pot with good drainage and a very porous mineral-based potting mix.
Watering: Keep dry in winter. Pot plants are quite wet-sensitively. Care must be taken with watering (Rot prone) and needs good drainage. Water sparingly during the growing season, keep very dry in winter.
Fertilization: Feed with a high potassium fertilizer in summer.
Hardiness: Usually it is recommended to overwinter this plant in a bright and warm greenhouse with at least 8-10° C , but it proved to be quite frost resistant (if kept dry it hardy as low as -10° C)
Exposure: Outside full sun or afternoon shade, inside needs bright light, and some direct sun.
Propagation: Direct sow after last frost, cuttings (if available).
Bibliography
Major references and further lectures
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David Hunt, Nigel Taylor “The New Cactus Lexicon” DH Books, 2006
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John Pilbeam (1999) “Mammillaria The Cactus File Handbook” Nuffield Press.
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Nathaniel Lord Britton, Joseph Nelson Rose “Cactaceae: Descriptions and Illustrations of Plants of the Cactus Family” vol. 4 The Carnegie Institution of Washington, Washington 1923
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Stuart Max Walters “The European Garden Flora: Dicotyledons (Part I)” Cambridge University Press, 1989
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Edward F. Anderson “The Cactus Family” Timber Press, 2001
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Fitz Maurice, B, Fitz Maurice, W.A., Hernández, H.M., Sotomayor, M. & Smith, M. 2013. Mammillaria formosa. In: IUCN 2013. “IUCN Red List of Threatened Species.” Version 2013.2. <www.iucnredlist.org>. Downloaded on 01 January 2014.
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