Mammillaria of the Month
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Photo: Plant in Cultivation: M heidiae. Copyright of Chris Davies 2009
Mammillaria heidiae is a species that is included in the Ancistracanthae but,
along with a related species Mammillaria zephyranthoides, it doesn't sit too
easily with the others of this Series. It is very
distinctive, a mostly flat bodies green plant coming from a large tap root, and
crowned by large yellow-green flowers.
At one stage it was considered to be of the Dolichothele subgenus, but that has now been largely discounted. It grows either as a solitary plant, but it will offset, and form small clumps, each head being anything up to 10cm across in cultivation. Each areole bears 16-24 glassy white bristly spines, and usually one or two brownish hooked central spines, though sometimes a plant with no centrals is encountered. It comes from the Mexican state of Puebla and is named after Frau Heidi Kraehenbuehl.
As might be expected from its large tap root, it is a species that to do well needs very good drainage, and especially careful watering when it starts to wake up in the Spring. Otherwise the root will start to rot, and the plant will become unsaveable other than by very quick grafting action.