Mammillaria guelzowiana
| Light | Bright light with a little shade from the harshest afternoon sun |
|---|---|
| Water | Very sparingly; allow to dry out completely between waterings, dry rest in winter |
| Soil | Extremely free-draining, mostly mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing and dry when cold; USDA zones 9b–11 |
| Propagation | Seed and offsets |
| Toxicity | Non-toxic to cats and dogs |
Mammillaria guelzowiana is a small, soft-bodied pincushion cactus from northern Mexico, cloaked in feathery white spines and crowned each summer by some of the largest flowers in the whole genus. Its silky, plumose radial spines partly hide its central spines, one of which is characteristically hooked, and its enormous silky-magenta blooms make it a prized — though notoriously rot-prone — collector's plant. It was long placed in the segregate genus Krainzia.
Description
Mammillaria guelzowiana forms a soft, more or less globular body a few centimetres across, sometimes remaining solitary and sometimes offsetting to build a small cluster with age. The stem is soft-fleshed rather than firm, and the tubercles are tipped with dense areoles that produce a mass of fine, hair-like white radial spines. These plumose radials are soft and feathery to the touch and give the plant a woolly, almost fuzzy silhouette.
Set among the radials are one to several longer central spines, yellowish to reddish-brown, one of which is distinctly hooked at the tip — a feature that catches on fingers and clothing. The great glory of the species, however, is its flowers: broad, silky, deep magenta-pink blooms that are exceptionally large for a Mammillaria, opening in a ring near the crown in late spring and summer and nearly eclipsing the body of the plant.
Distribution and habitat
The species is native to the state of Durango in northern Mexico, where it grows on rocky ground and among grasses in arid, well-drained sites. As with most Mexican cacti it is protected in habitat, and — like the whole family — is covered by CITES listing; nursery-propagated plants are widely available and are the only ones that should be bought or traded.
Cultivation
Mammillaria guelzowiana has a reputation for being tricky, and the reason is almost always its softness and its intolerance of excess moisture. Grow it in a very gritty, sharply draining, mostly mineral mix in a pot that dries quickly, and give it bright light with just a little shading from the fiercest afternoon sun to keep the plumose spines dense and white.
Water only when the soil has dried out completely, and err firmly on the side of underwatering — the soft body rots at the slightest provocation, particularly if water sits around the base or in the woolly crown. Keep the plant completely dry and cool through winter; this dry rest both prevents rot and encourages the spectacular flowering. Many growers keep this species on their own roots but with extra-lean soil, while others graft it onto a hardy rootstock to sidestep the rot problem entirely. See Watering and Repotting for general technique.
Propagation
Propagation is by seed or, where plants have clustered, by removing offsets. Seed is sown on a warm, mineral surface kept humid until germination, then grown on cautiously with careful watering. Offsets should be allowed to callus before being potted into a lean mix and kept barely moist until rooted, since freshly detached pieces of such a soft species rot easily.
Common problems
- Rot — by far the commonest cause of loss; overwatering, a slow-draining mix, or water lodging in the crown quickly turns the soft body brown and mushy.
- Etiolation — too little light makes the body stretch and pale and thins the feathery spination.
- Pests — mealybugs love to hide in the dense wool and among the tubercles, and red spider mites can bronze the skin; the plumose spines can make early infestations easy to miss.
See also
- Mammillaria — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — seed · Propagation — offsets