Oreocereus
Oreocereus is a small genus of columnar cacti native to the high Andes of Peru, Bolivia, Chile and Argentina. The name means "mountain Cereus", and the plants are famous for the long, white, woolly hairs that cloak their stout, spiny stems — a shaggy coat that shields them from fierce alpine sun by day and biting cold by night. This appearance has earned them the affectionate common name old man of the Andes.
Description
Oreocereus are slow-growing, erect to sprawling columnar cacti, usually branching from the base to form clumps of stems rather than tall single trunks. The ribbed green stems are armed with strong spines — often long, stiff and sometimes brightly coloured in yellow, amber or red — and are veiled to varying degrees in fine white hair. In the hairiest species this fleece can almost hide the body of the plant, while in others it gathers mainly around the growing tip and areoles.
The flowers are tubular and slightly asymmetric (zygomorphic), emerging near the stem tips in shades of pink, rose and red. Their shape and colour reflect pollination by hummingbirds in habitat. Flowers are typically followed by rounded, hollow fruits.
Distribution and habitat
The genus is a true high-altitude specialist, growing on rocky slopes and among boulders in the central Andes, frequently well above 2,000 metres. Here plants endure intense ultraviolet light, wide day-to-night temperature swings and cold, dry winters — conditions their hairy, well-spined stems are beautifully adapted to. The distribution spans southern Peru and Bolivia down into northern Chile and northwestern Argentina.
Notable species
- Oreocereus celsianus — perhaps the classic "old man of the Andes", with pale hair and strong spines
- Oreocereus trollii — a shorter, extremely woolly species, densely wrapped in white hair
- Oreocereus doelzianus — once placed in the genus Morawetzia; produces striking deep pink to red flowers
- Oreocereus leucotrichus — a Peruvian and Chilean species with abundant white wool
- Oreocereus hendriksenianus — noted for reddish spines contrasting with pale hair
Botanical treatments vary, and some plants have been shuffled between Oreocereus and the closely related Borzicactus; a few names once listed under Borzicactus belong here.
Cultivation
Oreocereus are rewarding for growers who can give them strong light and a genuinely dry winter rest. Plant them in a very free-draining, mostly mineral mix and give the brightest position available — full sun encourages dense hair and sturdy spines, whereas shade produces weak, sparsely woolly growth.
Water generously during the warm growing season, always allowing the mix to dry fully between waterings, then keep the plants dry and cool through winter. Because they come from cold mountains, mature plants tolerate low temperatures far better than most cacti provided they are kept dry — winter wet at low temperatures is the quickest route to rot. See Watering and Repotting for general technique. Growth is slow but steady, and old clumping specimens are handsome, characterful plants.
In cultivation
The long white hair is the whole appeal, so growers prize forms with the densest, cleanest fleece. That same hair can trap dust and, unfortunately, hide early pest infestations such as mealybugs, so it pays to part the wool occasionally and check the areoles. Oreocereus are also grown from seed by enthusiasts, though germination and early growth are unhurried.
Propagation
Fresh seed is the usual method for the genus and gives the most natural, well-branched plants; sow onto a warm, gritty surface kept humid (see Propagation — seed). Clumping species can also be increased by removing rooted or unrooted basal branches as cuttings, allowing the cut surface to callus before potting into a barely moist mineral mix.
See also
- Borzicactus — a closely related Andean genus
- Soil and potting mix · Watering · Repotting · Propagation — seed · Propagation — cuttings · Pests and diseases