Mammillaria herrerae
| Light | Bright light with a little shade from harsh afternoon sun |
|---|---|
| Water | Sparingly; let the soil dry fully between waterings, dry rest in winter |
| Soil | Very free-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 9b–11 |
| Propagation | Seed (primary); often grafted to speed growth |
| Toxicity | Non-toxic to cats and dogs |
Mammillaria herrerae is a tiny, solitary, globular cactus from central Mexico so densely wrapped in fine white radial spines that a healthy plant looks like a little snowball or golf ball cactus. Despite its small size it produces surprisingly large, showy pink flowers, and it is one of the most sought-after — and most endangered — members of the genus Mammillaria.
Description
Mammillaria herrerae forms a small, near-spherical body usually only 2–4 cm across, typically staying solitary rather than clustering. The surface is built from many small tubercles, each carrying an areole crowded with numerous short, fine, white radial spines. These spines lie flat and interlock so completely that they hide the green body beneath, giving the plant its characteristic soft, woolly, golf-ball appearance.
The flowers are large in proportion to the plant — broad, funnel-shaped and pink to pinkish-magenta, opening around the crown in a ring. Against the white spination the bloom is strikingly showy, which is a large part of the species' appeal to collectors.
Distribution and habitat
The species is endemic to a very restricted area in the state of Querétaro in central Mexico, where it grows on rocky, calcareous ground in arid scrub. Its natural range is small and fragmented.
Wild populations have been severely reduced by illegal collection and habitat disturbance, and the species is regarded as critically endangered in habitat. Like the whole cactus family it is listed under CITES Appendix II. Nursery-propagated plants are widely and legally available, however; collecting from the wild is both illegal and a genuine threat to the species' survival, so responsible growers buy only cultivated stock.
Cultivation
Mammillaria herrerae has a reputation for being tricky, and the usual cause of loss is moisture sitting around the roots. Grow it in a very gritty, mostly mineral mix in a small pot, in bright light with just a little protection from the fiercest afternoon sun to keep the spination dense and white. Water thoroughly only once the soil has dried out completely, then let it dry again; keep the plant dry and cool through winter, which both prevents rot and encourages spring flowering. See Watering and Repotting for general technique.
Because the species is slow and can be fussy on its own roots, many growers keep it grafted onto a hardier rootstock, which greatly speeds growth and reduces losses. Grafted plants grow faster and fatter but often look a little different from a lean, own-root specimen.
Propagation
Seed is the standard and most reliable method. The fine seed is sown on a warm, mineral surface kept humid until germination, and seedlings are grown on carefully. The species rarely offsets, so vegetative propagation from pups is uncommon; where quicker results are wanted, seedlings are frequently grafted. See Propagation - seed for a full walkthrough, and Propagation - offsets for the occasional clustering plant.
Common problems
- Rot — almost always from overwatering or a slow-draining mix; the plant softens and discolours, often from the base.
- Etiolation — too little light makes the body elongate and the spination thin and sparse, spoiling the golf-ball look.
- Pests — red spider mites and mealybugs can hide among the dense spines; watch for fine webbing or white fluff in the areoles. See Pests and diseases.
See also
- Mammillaria — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation - seed · Repotting