Mammilloydia
Mammilloydia is a monotypic genus of cactus containing the single species Mammilloydia candida, the snowball or snowball pincushion cactus, from the deserts of northeastern Mexico. It was segregated from the huge genus Mammillaria on the basis of distinctive seed and areole characters, though a good many botanists now sink it straight back into Mammillaria — so you will meet the same plant under both names in the trade.
Description
Being a genus of one, Mammilloydia is best described through its sole species. Plants form a solitary or slowly clustering globe, blueish-green beneath a dense armour of chalk-white radial spines that all but hide the body — the source of the common name "snowball". Like true Mammillaria, the body is built from spiralling tubercles rather than continuous ribs, with flowers and offsets arising from the woolly axils between them. Small pinkish to whitish flowers open in a ring near the crown.
The features that set Mammilloydia apart from Mammillaria are technical rather than obvious to the eye: they rest chiefly on the seed coat and on details of the areoles and tubercle arrangement. Franz Buxbaum used seed characters to raise the genus; the seeds are now generally described as having a smooth, hard, essentially non-pitted testa (seed coat). Later workers, weighing molecular evidence, have often folded the genus back into Mammillaria. For the grower, the takeaway is simple — it looks and behaves like a white-spined pincushion cactus.
Distribution
Mammilloydia candida grows on limestone in the Chihuahuan Desert region of northeastern Mexico, across the states of Nuevo León, Tamaulipas, San Luis Potosí and Coahuila, at roughly 500–2,500 m elevation. It favours well-drained, calcareous ground — rock crevices and gravelly flats — and in habitat it is often found tucked among xerophytic shrubs that give it some shade rather than out in the open.
Notable species
- Mammilloydia candida — the only species; the white-spined "snowball" cactus described above. Depending on the author you follow, it may also appear as Mammillaria candida.
Cultivation
Care follows the same lines as a typical white-spined Mammillaria. Grow it in a very free-draining, mostly mineral mix in a snug pot, and give it plenty of bright light — strong light keeps the spination dense and snow-white, whereas too little light thins the armour and dulls the plant. Water thoroughly once the soil has dried right out through the warm months, then keep it dry and cool over winter to encourage a good spring flush of flowers and to guard against rot. As with most desert cacti from limestone country, it appreciates a little added grit or crushed limestone and resents standing damp. See Watering and Repotting for general technique.
Propagation is by seed, which germinates readily on a warm mineral surface, or by removing rooted offsets from clustering plants. Slow or awkward seedlings are sometimes grafted to speed them along, but the species grows perfectly well on its own roots.
Hobby notes
In collections and nursery labels you will very often see this plant sold as Mammillaria candida rather than Mammilloydia candida — both names refer to the same cactus, and the choice reflects which classification a given grower or catalogue follows. It is a handsome, undemanding pincushion prized for its clean white spination, and there are no significant named cultivars; growers instead select for particularly dense, bright-white forms. Watch for the usual pincushion troubles — red spider mites and mealybugs tucked among the spines, and rot from overwatering or a slow mix.
See also
- Mammillaria — the large genus into which this plant is often merged
- Mammilloydia candida — the single species
- Soil and potting mix · Watering · Propagation — seed · Propagation — offsets