Mammillaria pilcayensis
| Light | Bright light, including some direct sun; a little protection from the harshest afternoon glare |
|---|---|
| Water | Moderate in the growing season, allowing the mix to dry fully between waterings; keep dry and cool in winter |
| Soil | Fast-draining, gritty mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 9b–11 |
| Propagation | Offsets and stem cuttings; also seed |
| Toxicity | Non-toxic to cats and dogs |
Mammillaria pilcayensis is a clustering, cylindrical cactus from south-central Mexico, now generally treated as a subspecies of the widespread Mammillaria spinosissima (Mammillaria spinosissima subsp. pilcayensis). It belongs to the spiny spinosissima group and is grown for its dense, bristly spines — usually golden-yellow, sometimes flushed reddish — that sheathe each stem, and for its readiness to cluster and arch over the edge of the pot, which makes it a rewarding and forgiving plant for the windowsill grower.
Description
Mammillaria pilcayensis forms clusters of slender cylindrical stems that begin upright but soon arch over and trail, lengthening to as much as 30–50 cm with age. As in the rest of the genus, the body is built from small conical tubercles arranged in neat spirals rather than continuous ribs. Each tubercle carries an areole bearing numerous fine radial spines together with several slightly stouter central spines, cloaking the stem in a dense, brush-like cover that is typically golden-yellow, often flushed reddish or with darker tips. This crowded, bristly spination — the source of the common name "bristle brush" — is heavier than in many relatives and helps distinguish the plant within the spinosissima complex.
Small funnel-shaped flowers appear in a ring around the upper stems in spring, purplish-pink to magenta and only about 2 cm across, and are followed by slender club-shaped berry-like fruits.
Distribution and habitat
The plant is restricted to a small area on the border of Guerrero and the State of Mexico, in and around the Barranca de Pilcaya (from which the name derives) and the adjoining Barranca de Malinaltenango. It grows on calcareous rocky slopes and cliff faces in seasonally dry scrub and tropical dry forest, at roughly 600–1,500 m, rooting in thin, sharply drained mineral soils among rock. Like all of Mammillaria and the wider cactus family, it is subject to habitat pressures; nursery-grown plants are widely available and are the responsible way to obtain it.
Cultivation
This is one of the easier mammillarias and a good choice for the beginner. Grow it in a very free-draining, mostly mineral mix in a pot that is not too large, and give it as much bright light as you can — plenty of light keeps the clump compact and brings out the richest spine colour, whereas shade produces pale, drawn growth. Water moderately once the mix has dried through during the warm months, then reduce sharply and keep the plant dry and cool over winter; this winter rest guards against rot and encourages the spring ring of flowers. See Watering and Repotting for general technique.
As the clump matures the stems arch and trail over the pot's edge, so plants are well shown in a raised or half-height pot that lets the stems hang. Overwatering, especially in cool or dull conditions, is the main thing to avoid.
Propagation
Because the plant clusters freely, the simplest method is to detach an offset or a healthy stem, let the cut surface callus for several days, and pot it into a barely-moist gritty mix until roots form. See Propagation — offsets and Propagation — cuttings. The species can also be raised from seed, though this is slower and less commonly needed given how readily it branches.
Common problems
- Rot — usually the result of overwatering or a slow-draining mix, particularly during the cool months; stems soften and discolour from the base.
- Etiolation — too little light stretches the stems and pales the spines, spoiling the compact, golden look.
- Pests — mealybugs can shelter deep among the tubercles and dense spines, and red spider mites may bronze the growing tips; inspect the crowded stems regularly (see Pests and diseases).
See also
- Mammillaria — the genus overview
- Mammillaria spinosissima — the species this plant belongs to
- Soil and potting mix · Watering · Propagation — offsets · Propagation — cuttings · Repotting