Oreocereus pseudofossulatus
| Light | Bright light to full sun; loves all the sun you can give it |
|---|---|
| Water | Moderate in the warm months, letting the mix dry between waterings; keep dry and cool in winter |
| Soil | Gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Tolerates cool nights; protect from hard frost, USDA zones 9b–11 |
| Propagation | Seed; occasionally from offsets or cuttings |
| Toxicity | Not known to be toxic to cats or dogs, though the stiff spines and bristly hair are a mechanical hazard |
Oreocereus pseudofossulatus is a columnar cactus from the Bolivian highlands, grown for its bold architectural form: stout ribbed stems clothed in strong spines and long white hair. Like its relatives in the genus Oreocereus — the "old men of the mountains" — it wraps itself in a woolly fleece that softens its fierce spination and lends the plant a shaggy, silver-haired look prized by collectors.
Description
Oreocereus pseudofossulatus forms erect, cylindrical stems that are typically solitary or branch from the base with age, reaching a bold, upright habit over many years. The stems are divided into prominent ribs bearing closely spaced areoles. From these areoles emerge stiff, needle-like spines — often longer central spines set among shorter radials — together with the copious white to greyish hair that is the hallmark of the genus.
The overall effect is strongly architectural: a firm green column banded with ribs, armed with spines, and veiled in a fleece of white wool that catches the light. As with other Oreocereus, the hair varies from plant to plant, and older specimens tend to develop the fullest, most silvered coats. Tubular flowers, when they appear on mature plants, push out near the stem tips in warm-season shades typical of the genus.
Distribution and habitat
The species is native to Bolivia, where it grows in the high Andes at considerable altitude. Plants of this group inhabit rocky slopes and open, exposed ground, rooting in lean mineral soils among stones. The dense hair is not merely ornamental — at these elevations it helps buffer the plant against intense mountain sunlight and the wide swings between hot days and cold nights.
Cultivation
Oreocereus pseudofossulatus is a rewarding grower for anyone who can give it sun and sharp drainage. Plant it in a very free-draining, mostly mineral mix and site it in the brightest position available; strong light keeps the growth compact and encourages the fullest development of the white hair. Thin, drawn growth and sparse wool are usually signs of too little light.
Water moderately through the warm growing season, letting the mix dry out between waterings, then keep the plant dry and cool over winter. This dry winter rest suits its montane origins, hardens the plant against rot, and helps mature specimens toward flowering. Being a high-altitude cactus it takes cool nights in its stride, but protect it from hard, wet frost. See Watering and Repotting for general technique.
Propagation
Seed is the most reliable route and yields the most naturally shaped plants; sow onto a warm, mineral surface kept lightly humid until germination, then grow the seedlings on hard in good light (see Propagation — seed). Where a plant offsets or a stem is available, cuttings can also be taken — allow the cut surface to callus thoroughly before setting it on barely-moist mineral mix to root. See also Propagation — offsets.
Common problems
- Rot — the usual cause of loss, almost always from overwatering, a slow-draining mix, or cold wet conditions in winter; stems soften and discolour from the base.
- Etiolation — too little light produces pale, narrow, drawn growth and a thin, disappointing coat of hair.
- Grubby hair — the white wool traps dust and can shelter pests; mealybugs in particular like to hide within it, so check under the fleece from time to time.
- Pests — mealybugs (white fluff among the wool and areoles) and red spider mites (fine webbing, bronzed skin) are the most common.
See also
- Oreocereus — the genus overview
- Soil and potting mix · Watering · Repotting
- Propagation — seed · Propagation — cuttings · Propagation — offsets
- Pests and diseases