Pilosocereus royenii
| Light | Full sun to bright light; acclimate gradually to avoid scorch |
|---|---|
| Water | Moderate in warmth; let the mix dry between waterings, keep drier and warmer in winter |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Frost-tender; keep above about 5 °C, USDA zones 10–11 |
| Propagation | Seed and stem cuttings |
| Toxicity | Non-toxic to cats and dogs, though spiny |
Pilosocereus royenii is a tree-like columnar cactus native to the Caribbean, where it is a common sight on rocky, sun-baked coastal slopes and islands. It forms a branching, blue-green plant clothed in a waxy bloom, and is grown by collectors for its statuesque form and easy, fast-growing habit. Like others in the genus Pilosocereus, mature flowering branches develop tufts of long, hair-like bristles at the areoles that give the group its name.
Description
Pilosocereus royenii grows into a shrubby to small tree-like cactus, branching from near the base or from a short trunk and reaching a few metres tall in habitat. The stems are cylindrical and distinctly blue-green to grey-green, coated in a pale waxy bloom that rubs off to the touch and helps reflect the intense Caribbean sun. Each stem carries several prominent ribs lined with closely spaced areoles bearing clusters of stiff, yellowish to brown spines.
As branches mature they develop a flowering zone, or pseudocephalium, where the areoles produce dense tufts of long, woolly, hair-like bristles. Nocturnal funnel-shaped flowers open here — pale, greenish to whitish and rather waxy — and are followed by fleshy, rounded fruit. As with many night-blooming columnar cacti, the flowers are adapted for pollination by bats and moths.
Distribution and habitat
The species occurs through the West Indies, particularly the Lesser Antilles, Puerto Rico and the Virgin Islands. It favours hot, exposed, low-elevation sites: rocky coastal hillsides, limestone outcrops and dry scrub, often growing among other drought-adapted plants in thin, gritty soils with excellent drainage and plenty of sun and salt-laden air.
Its natural toughness in these lean, exposed conditions is a good guide to its needs in cultivation — bright light, sharp drainage and warmth.
Cultivation
Pilosocereus royenii is an accommodating, relatively fast grower for a columnar cactus. Give it the sunniest position you can and a very free-draining, mostly mineral mix. Water reasonably through the warm growing season once the mix has dried, then reduce watering and keep the plant warm and largely dry over winter; it resents cold, damp roots. It is frost-tender, so in temperate climates it is best grown in a container that can be moved under cover before cold weather.
The waxy, glaucous bloom on the stems is easily marked by handling or by water spots, so try to water at the roots rather than over the body, and handle plants as little as possible. In too little light the stems may lose colour and grow thin and etiolated. See Watering and Repotting for general technique.
Propagation
The species grows readily from both seed and stem cuttings. Seed germinates well on a warm, moist mineral surface and produces even batches of seedlings. Cuttings of a stem segment should be allowed to callus for a week or more in a dry, shaded spot before being set on a barely-moist gritty mix to root. See Propagation — seed and Propagation — cuttings for full walkthroughs.
Common problems
- Rot — the usual cause of loss, from overwatering, cold-and-wet conditions or a slow-draining mix; stems soften and discolour.
- Marked bloom — the waxy glaucous coating is permanently smudged by fingerprints or hard-water spots; unavoidable but purely cosmetic.
- Etiolation — too little light produces pale, thin, weakly growth that loses the compact blue-green form.
- Pests — mealybugs (white fluff in the areoles) and scale are the common offenders; see Pests and diseases.
See also
- Pilosocereus — the genus overview
- Soil and potting mix · Watering · Propagation — seed · Propagation — cuttings · Repotting