Pilosocereus magnificus
| Light | Bright light to full sun; the strongest colour develops in intense light |
|---|---|
| Water | Moderate in the growing season, allowing the mix to dry between waterings; keep dry and cool in winter |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Warmth-loving; keep above freezing, USDA zones 9b–11 |
| Propagation | Seed, and stem cuttings |
| Toxicity | Not known to be toxic to cats or dogs |
Pilosocereus magnificus is a strikingly blue columnar cactus from eastern Brazil, prized by collectors for its intense waxy-blue skin set against dense tufts of white areolar hair. It is one of the most ornamental members of the genus Pilosocereus, the "hairy cereus" cacti, and its combination of powdery blue stems and long white wool makes it instantly recognisable in a collection.
Description
Pilosocereus magnificus is a shrubby to tree-like cactus that branches from near the base and can build into a small candelabra of upright stems with age. The stems are ribbed and clothed in a heavy, waxy bloom that gives them their signature chalky blue-green colour — the wax is a natural sunscreen, and plants grown in strong light show it most vividly.
Along the ribs the areoles carry short spines, usually amber to reddish-brown, and produce copious long white to greyish hairs. In mature plants this hair thickens conspicuously toward the top of the stem, forming a woolly flowering zone (a pseudocephalium) from which the flowers emerge. Like most Pilosocereus, the blooms are funnel- to bell-shaped, pale, and open at night, adapted for pollination by bats; they are followed by fleshy fruits.
Distribution and habitat
The species is endemic to Brazil, where it grows in the rocky, seasonally dry country of the interior — typical Pilosocereus habitat of exposed quartzite outcrops, cerrado and dry scrub. Plants root in shallow, gritty pockets among rock in bright, hot, well-drained situations, enduring a pronounced dry season. As with the whole cactus family, Pilosocereus is listed under CITES Appendix II; nursery-grown plants are freely and legally traded, while wild collection is not.
Cultivation
Pilosocereus magnificus is a rewarding grower that rewards heat and light. Give it the brightest position you can — full sun once acclimatised — as strong light is what draws out the deep blue bloom and keeps growth compact; in dim conditions the stems green up and stretch. Plant it in a very free-draining, mostly mineral mix and water moderately through the warm months, letting the mix dry out between drinks. See Watering for general technique.
Warmth is important: this is a tropical Brazilian species with little cold tolerance, so keep it above freezing and hold it dry and cool through winter to avoid rot. Handle the waxy stems as little as possible, since fingerprints and rubbing mark the delicate bloom. Repot into a slightly larger container as the plant fills its pot — see Repotting.
Propagation
The species is grown both from seed and from stem cuttings. Seed germinates readily with warmth and humidity on a mineral surface, giving genetically varied seedlings. Cuttings taken from a branch should be left to callus for a week or more in a dry, shaded spot before being set on barely-moist mineral mix to root; this is the quicker route to a sizeable plant and preserves the colour of a good clone.
Common problems
- Rot — the usual cause of loss, from overwatering, a slow-draining mix, or cold wet conditions in winter; stems soften and discolour from the base or a damaged point.
- Loss of blue colour and etiolation — too little light greens the stems and makes growth thin and elongated, losing the compact blue form.
- Marked bloom — the waxy coating is easily rubbed off by handling and does not regrow on old growth, so scuffs are permanent until new stem forms.
- Pests — mealybugs (white fluff, easily hidden among the areolar hair) and red spider mites (fine webbing, bronzed patches) are the usual offenders. See Pests and diseases.
See also
- Pilosocereus — the genus overview
- Soil and potting mix · Watering · Repotting
- Propagation — seed · Propagation — cuttings · Pests and diseases