Mammillaria sheinvariana
(Syn: Mammillaria crinita)

Stem covered by numerous hairlike radial spines,  giving the plant a shaggy appearance.
 

Morphology (Identifying Characteristics): It is a small plant  that forms irregular clumps.
Stem: About 5 cm diameter and 2–3.5cm high.
Radial spines:  Numerous hair-like spines give the plant a shaggy appearance.
Central spines: Not usually present, but, if so, they are 9–16 mm long and straight, never hooked. (At first glance the plant has quite a strong resemblance to M. bocasana, but a closer inspection reveals the absence of hooked centrals)
Root:  It has a thick tuberous root system
Flowers:  Salmon pink.
Blooming season (Europe): May-June

Taxonomy: This plant is a member of the Mammillaria crinita complex (Stylothele Series). Only some authors consider M. sheinvariana to be a good species; the others classify it as M. crinita (e.g. Fritz Maurice accepts the individuality of the new plant but considers it a subspecies of M. crinita.)
 

Photo of conspecific taxa, varieties, forms and cultivars of plants belonging to the Mammillaria crinita complex  (This taxon has lots of synonyms (like most mammillaria) with several controversial varieties and subspecies):

• M. brevicrinita (M. crinita)
• M. duwei (m. crinita ssp. duwei)
• M. glochidiata var. xiloensis (M. crinita)
• M. painterii forma mostruosa (M. crinita fa. mostruosa. )
• M. sheinvariana (M. crinita)
• M. trichacantha (M. crinita)
• M. wildii forma cristata (M. crinita subsp. wildii fa. cristata)

Scientific Name: Mammillaria sheinvariana Ortega & Glass  1997.
Published in: Guia para la Identificacion de Cactaceas Amenazadas de Mexico. (Identification Guide to the Threatened Cacti of Mexico). CANTE, A.C., Guanajuato, Mexico.

Distribution: Zimapan, Queretaro, Mexico

Habitat: The whole  habitat of this plant (discovered  only in 1997) disappeared under the water of a man-made dam.  It is extinct in nature. The British Cactus and Succulent Society published a very interesting online article about this new rare  plant:

Click here to see the pdf document.

Copyright "British Cactus and Succulent Journal" Vol 21 (1) 45-48

Cultivation:  It has a thick root and is susceptible to over-watering.  Sometimes it is grafted to avoid root rot problems.  It likes warmth (recommended minimum winter temperature 5° C), but if kept perfectly dry it can easily survive at winter night temperatures below 0° C  (in our greenhouse no damage at  -10° C for a few hours in the winter of 2002-2003).  Suited for sunny-bright exposure; it can tolerate light shade, likes airy exposures.  It needs a deep pot and good drainage to accommodate its tuberous root system.  Keep dry in winter.
Pests & diseases:   M. sheinvariana is especially prone to rot, therefore, under-pot in a smaller container filled with very porous compost.

Propagation: Seeds or graft. Seeds can be sown in the spring or summer. The seedlings should not be disturbed until they are well rooted, after which they can be planted separately in small pots.