Mammilloydia candida
| Light | Bright light; full sun to light afternoon shade |
|---|---|
| Water | Sparingly; allow to dry fully between waterings, dry rest in winter |
| Soil | Very free-draining mineral mix, slightly alkaline (see Soil and potting mix) |
| Temperature | Keep above freezing; USDA zones 9b–11 |
| Propagation | Seed; offsets from older clustering plants |
| Toxicity | Non-toxic to cats and dogs |
Mammilloydia candida is a globular, densely white-spined cactus from north-central Mexico, widely grown for the neat blanket of pure-white radiating spines that gives it the common name snowball cactus. It is treated by many botanists as the sole species of the monotypic genus Mammilloydia, though it is just as often listed under its older name Mammillaria candida and sits close to the huge genus Mammillaria.
Description
Mammilloydia candida forms a firm, rounded to shortly cylindrical body, typically 6–9 cm across and eventually up to about 14 cm tall, that is solitary when young and slowly clusters with age. The surface is covered in spiralling tubercles, each tipped by an areole bearing numerous fine, chalk-white radial spines that overlap to cloak the plant almost completely — the feature behind the "snowball" name. A few slightly stouter central spines, sometimes faintly pink- or brown-tipped, sit among the radials.
The plant differs from typical Mammillaria chiefly in the structure of its seeds, which is why it is often separated into its own genus. Flowers appear in a ring near the crown, opening pinkish-white with darker midstripes, followed by small reddish fruits.
Distribution and habitat
The species grows in the arid highlands of north-central Mexico, in states such as San Luis Potosí, Nuevo León, Tamaulipas and Coahuila. It is characteristically found on limestone, rooting in rocky, gritty ground among sparse desert scrub, which accounts for its preference for lean, alkaline, sharply drained substrates in cultivation.
Cultivation
Mammilloydia candida is a rewarding but somewhat exacting plant that rots easily if kept damp. Grow it in a very free-draining, mostly mineral mix — a little added limestone or crushed oyster shell suits its love of alkaline soils — in a snug pot with plenty of light. Water thoroughly only when the soil has dried right through, then allow it to dry again; keep the plant dry and cool over winter to firm it up and encourage flowering. Its dense white spination can hide the early signs of rot or pests, so check the body periodically. See Watering and Repotting for general technique.
Propagation
Seed is the usual method: sown on a warm, gritty surface kept lightly humid, the seedlings are slow but steady. Older plants that have begun to cluster can also be increased by removing rooted offsets, though the species offsets far less freely than many of its Mammillaria relatives. See Propagation — seed for a full walkthrough.
Common problems
- Rot — the commonest cause of loss, almost always from overwatering or a mix that holds moisture; the body softens from the base or crown.
- Hidden pests — red spider mites and mealybugs can shelter unseen within the thick spine cover, so inspect regularly for webbing or white fluff.
- Etiolation — too little light makes the body elongate and the spine cover thin and open, spoiling the tidy globular shape.
See also
- Mammilloydia — the genus overview
- Mammillaria — the closely related genus under which this plant is often listed
- Soil and potting mix · Watering · Propagation — seed · Propagation — offsets · Repotting