About Mammillaria albiflora (Werderm.) Backeb.
Mammillaria albiflora (Werderm.) Backeb. usually grows singly and only rarely forms clusters. Its somewhat cylindrical stems can reach heights of over 5 centimeters, with diameters between 1 and 2 centimeters, but these stems are mostly hidden beneath dense spines. Its small tubercles do not produce milky sap, and the plant's axils are bare. This species has no central spine, instead it bears 60 to 80 short, white intertwined radial spines. Its flowers are white with a faint pink tinge; they can grow up to 3.5 centimeters long, and reach about 2.5 centimeters in diameter. The fruit of this cactus is hidden under the spines but sits outside the main plant body. Its seeds are black, and require careful handling to locate. This species is native to Guanajuato, a Mexican state. It occurs south of Pozos, at altitudes between 2,160 and 2,200 metres (7,090 and 7,220 ft), growing along the road to San José Iturbide and at La Calera. These locations are roughly 50 km or more away from the range of the related species M. herrerae. It grows on sloping calcareous rock in a semi-desert habitat. Because it only occurs in one location with a very limited range and its population is continuously declining, the International Union for Conservation of Nature (IUCN) lists Mammillaria albiflora as Critically Endangered. The main threat to its survival is illegal collection, carried out by both amateur plant hobbyists and commercial collectors. A section of its known location was fenced to protect the species, but the fence was breached soon after it was installed. Between 1993 and 2013, the total population fell from approximately 10,000 individuals to approximately 5,000 individuals. Mammillaria albiflora is illegally collected or commercially cultivated to use as an ornamental plant. It is propagated around the world and can be found in international trade. This cactus is difficult to cultivate; it appears to dislike peat and acidic humus in potting mixes. A potting mixture that includes some limestone is likely beneficial for its growth. For successful growth and especially for flowering, the plant requires maximum sun exposure, which is crucial.
