Mammillaria plumosa
| Light | Bright light with some protection from harsh afternoon sun |
|---|---|
| Water | Sparingly; let the mix dry fully between waterings, keep nearly dry in winter |
| Soil | Very free-draining, gritty mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; broadly USDA zones 9b–11 |
| Propagation | Offsets (easiest); seed |
| Toxicity | Non-toxic to cats and dogs |
Mammillaria plumosa is a low, mound-forming cactus from northeastern Mexico, famous for the soft, downy plumes that clothe every areole and hide the plant beneath a fleece of white. Commonly called the feather cactus, it clusters into gentle cushions that can look more like a snowball or a patch of moss than a spiny cactus. It is one of the most beloved members of the huge genus Mammillaria and a firm favourite with collectors.
Description
Mammillaria plumosa is a soft-globular cactus that offsets freely to build low, dense clusters, often 30 cm or more across in a happy old plant. Each individual head is small — typically only a few centimetres wide — and is made up of spiralled tubercles, in the classic Mammillaria fashion, rather than continuous ribs.
The plant's signature feature is its spines. What would be stiff radials in most cacti are here modified into fine, feathery ("plumose") white spines that branch like tiny feathers, softening the whole surface into a woolly, touchable-looking down. This fleece is not just decorative: in habitat it shades the body from fierce sun and helps buffer temperature. Small flowers, usually greenish-white to yellowish or cream, appear low among the plumes in autumn or early winter and can be easy to miss under all that fluff.
Despite the soft appearance, resist the urge to handle it — the plumes mat and discolour with oils from fingers, and trapped moisture invites rot.
Distribution and habitat
The feather cactus grows in the states of Coahuila and Nuevo León in northeastern Mexico, where it is found on limestone — clinging to cliff faces, rocky outcrops and steep, well-drained slopes. Its natural home is hot and bright with sharp drainage, and the dense white covering reflects that exposed, sun-baked habitat.
Cultivation
Mammillaria plumosa is not difficult, but like most fleecy, tubercled Mammillaria it is unforgiving of excess water sitting in its plumes or around its neck. Grow it in a very gritty, mostly mineral mix, ideally with a little added limestone to suit its natural substrate, in a pot no larger than it needs.
Give it bright light — full sun in cooler climates, with a touch of shade from the most intense midsummer afternoon sun to keep the fleece bright white rather than scorched. Water thoroughly only once the mix has dried right out, and always water at the soil, not over the plant, so water does not pool in the plumes. Through winter keep it cool and nearly dry; a dry, cool rest both prevents rot and helps trigger the autumn/winter flowering. See Watering and Repotting for general technique.
Propagation
Because it clusters so readily, the easiest route is division: gently separate rooted offsets from the cushion, let any cut surface callus for a few days, and pot up into the same gritty mix. See Propagation — offsets and Propagation — cuttings. The species also grows well from seed, which is how growers raise large numbers of plants, though seedlings are slow in their first year.
Common problems
- Rot — by far the biggest risk, usually from overwatering, a mix that holds too much moisture, or water trapped in the fleece; heads soften and brown from the base.
- Discoloured or matted plumes — caused by overhead watering, dust, or handling; keep water off the top and site the plant where it stays clean and dry.
- Etiolation — too little light makes heads stretch and the covering thin, so the plant loses its tight, snowball form.
- Pests — mealybugs love to hide deep among the plumes where they are hard to spot; red spider mites can also take hold in hot, dry, still air. See Pests and diseases.
See also
- Mammillaria — the genus overview
- Soil and potting mix · Watering · Repotting · Propagation — offsets · Pests and diseases