Mammillaria of the Month

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Mammillaria xanthina

This month’s Mammillaria is something of a mystery plant. Mammillaria xanthina was first reported in 1923 by Britton and Rose, as being from near Monte Mercado, Durango. Despite diligent searches since then it was not until 2007 that in the loose-leaf album of the German Mammillaria Society (AfM) that the rediscovery by Marion and Rudi Schumacher was published. The plants were found north-west of Durango, though the exact location was not given at that time, and conform pretty well to the original description. The plants were single or offsetting, 8-15cm in diameter and up to 25cm tall. It has 8-17 short mainly white radial spines, 3-5mm long, and 1-2, seldom 3, central spines, 5-6mm long, brown, the flowers being yellow. Since then, other discoveries have been made in the northern reaches of the Rio Piaxtla in Sinaloa. Where this plant fits into the Mammillaria Classification remains somewhat unclear, though the New Cactus Lexicon dismisses it as a synonym of Mammillaria canelensis.  However, this species is given an uncertain status, suggesting that it is actually just another form of M. standleyi. Given the geographic locations of these plants this doesn’t seem to be obvious choices. Those who stayed for the Mammillaria Society Lecture at Witney on the 15th July 2012 will have heard Wolfgang Plein give his views on the relationship between the plants in North-West Mexico, making a strong argument for giving status to groups of plants from specific distribution areas, largely related to the drainage systems that exist in this large region. This certainly has given much food for thought, and a need for a these preliminary conclusions to be confirmed and documented. Seed under the name of M. xanthina, without location data or any source, from a Czech nursery were sown in 2010 and so far would appear to be close to the description, but seed and plants from the known recent collections is eagerly awaited. M. xanthina? from northwest of Durango                                      M. xanthina? seedling, from undocumented Czech seed.