Mammillaria nivosa
| Light | Bright light to full sun; tolerates some shade |
|---|---|
| Water | Sparingly; allow to dry fully between waterings, dry rest in winter |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; USDA zones 10–11 |
| Propagation | Offsets (primary); seed |
| Toxicity | Non-toxic to cats and dogs |
Mammillaria nivosa is a clustering, low-growing cactus native to the islands of the Caribbean, and one of the very few members of the large genus Mammillaria to occur naturally in the West Indies. Its rounded green stems bear stiff, golden-amber spines set in dense tufts of white wool, a combination that gives the plant its snowy, honey-tipped look and the common name woolly nipple cactus (the epithet nivosa meaning "snowy").
Description
Mammillaria nivosa begins as a solitary globe but soon offsets freely, building up into low mounds or dense clumps of many heads with age. Individual stems are roughly globular to short-cylindrical, several centimetres across, and firm and dark green. As with other members of the genus, the body is covered in spirally arranged tubercles (the "nipples" of the common name) rather than continuous ribs.
The areoles at the tips of the tubercles carry stiff, straight radial and central spines that range from golden and amber to honey-brown, and the axils between the tubercles are filled with conspicuous white wool — heaviest around the crown, where it can give the growing point a snowy cap. Small cream to pale-yellow flowers open in a ring near the top of each stem, followed by the smooth reddish berries typical of Mammillaria.
Distribution and habitat
The species is found through parts of the Caribbean, including the Bahamas, the Greater and Lesser Antilles and nearby islands, where it grows in hot, sunny, coastal and rocky situations. Plants typically root in thin soils, crevices and gritty pockets over limestone, often fully exposed to strong sun, salt air and long dry spells. This West Indian distribution is unusual for the genus, whose diversity is centred far to the west in Mexico.
Cultivation
Mammillaria nivosa is an easygoing, sun-loving cactus that rewards a bright position and a lean, sharply drained home. Grow it in a very free-draining, mostly mineral mix and give it as much light as you can — the spination colours up best and the plant stays compact in strong sun. Water thoroughly once the soil has dried out completely, then let it dry again; keep the plant dry and cool through winter to prevent rot and encourage flowering. Coming from a warm island climate, it dislikes prolonged cold and wet, so protect it from frost. See Watering and Repotting for general technique.
Propagation
Because the plant clusters so readily, the easiest method is division: detach rooted offsets, let the cut surfaces callus for a few days, and pot them into a gritty mix. Seed is also straightforward, germinating on a warm, humid mineral surface and giving large batches of seedlings. See Propagation — offsets and Propagation — seed for full walkthroughs.
Common problems
- Rot — the most common cause of loss, almost always from overwatering or a slow-draining mix, especially in cool weather; stems soften and discolour from the base.
- Etiolation — too little light makes stems pale and stretch, and the spines come in weaker and less colourful.
- Pests — mealybugs (white fluff, easily confused with the plant's own axil wool) and red spider mites (fine webbing, bronzed skin) are the usual culprits. See Pests and diseases.
See also
- Mammillaria — the genus overview
- Soil and potting mix · Watering · Propagation — offsets · Propagation — seed · Repotting