Mammillaria candida
| Light | Bright light; full sun to very light shade, especially good colour in strong light |
|---|---|
| Water | Sparingly; allow the mix to dry fully between waterings, keep dry in winter |
| Soil | Very gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 9b–11 |
| Propagation | Seed; occasionally by separating offsets from clustering plants |
| Toxicity | Non-toxic to cats and dogs |
Mammillaria candida is a small, globular to shortly cylindrical cactus densely clothed in fine, radiating white spines that all but hide the green body beneath, giving it the affectionate common name snowball pincushion. Native to arid limestone country in north-central Mexico, it is distinctive enough that botanists have sometimes segregated it into its own monotypic genus, Mammilloydia, though most growers still know and label it as a Mammillaria.
Description
Mammillaria candida forms a firm, rounded body up to roughly 6 cm tall and about 5–8 cm across, solitary at first but often clustering into tidy clumps with age. As in all Mammillaria, the surface is built from spirally arranged tubercles rather than continuous ribs, and the sap is watery rather than milky when a tubercle is broken — one of the features used to distinguish this species from its relatives.
Each areole bears numerous slender radial spines, typically fifty or more, chalky white and radiating flat against the body so that they overlap into a soft, snowy covering. A few slightly stouter central spines, sometimes faintly pink- or brown-tipped, sit at the crown of each tubercle. Small pink to purplish-pink flowers with paler margins appear in a ring near the top of the plant in spring and summer, followed by dry reddish fruits.
Distribution and habitat
The species is native to north-central Mexico, in states such as San Luis Potosí, Zacatecas, Coahuila and Nuevo León. It grows in hot, dry scrub and grassland, characteristically rooted in gravelly or rocky limestone soils on exposed slopes and flats, where sharp drainage and intense sunlight are the norm.
Cultivation
Mammillaria candida is a rewarding but somewhat rot-prone species that repays a lean regime. Grow it in a very free-draining, mostly mineral mix with plenty of grit, in the brightest position you can offer — strong light keeps the spination dense and white and the body compact. Water thoroughly only when the mix has dried right out, then let it dry again; the dense spine cover can hold moisture against the body, so err on the side of underwatering.
Keep the plant dry and cool through winter, which both prevents rot and encourages the spring flush of flowers. Its limestone origins mean it appreciates a mineral, slightly alkaline substrate and dislikes sitting in rich, water-retentive compost. See Watering and Repotting for general technique.
Propagation
Seed is the main method and germinates readily on a warm, gritty surface kept lightly humid; see Propagation — seed. Clustering plants can also be increased by carefully removing offsets once they have their own roots, then allowing the cut surface to callus before potting — see Propagation — offsets. Grafting is sometimes used to speed up slow or difficult seedlings.
Common problems
- Rot — the usual cause of loss, almost always from overwatering, a slow-draining mix, or moisture trapped under the dense spines; the body softens and discolours from the base or crown.
- Etiolation — too little light makes the body pale and stretch upward and thins the spination, spoiling the plant's compact, snowball form.
- Pests — red spider mites and mealybugs can hide among the crowded spines and in the tubercle axils, so inspect regularly (see Pests and diseases).
See also
- Mammillaria — the genus overview
- Soil and potting mix · Watering · Repotting
- Propagation — seed · Propagation — offsets · Grafting