Eriosyce occulta
| Light | Bright light; some protection from the harshest midday sun |
|---|---|
| Water | Very sparingly; keep dry through its long dormancy |
| Soil | Extremely free-draining, gritty mineral mix (see Soil and potting mix) |
| Temperature | Keep frost-free; enjoys cool, dry winters |
| Propagation | Seed (primary) |
| Toxicity | Not known to be toxic to cats or dogs |
Eriosyce occulta is a small, cryptic cactus from the coastal Atacama Desert of northern Chile that retreats below the soil surface during drought, leaving only its flattened crown visible among the surrounding gravel. Prized by collectors of miniature geophytic cacti, it belongs to a group of dwarf Chilean species once placed in the genera Neochilenia and Thelocephala and now folded into Eriosyce.
Description
Eriosyce occulta is a solitary, small-bodied cactus with a rounded to flattened top and a stout, tapering taproot that makes up much of the plant. In cultivation the body sits proud of the soil, but in habitat the plant can contract deep into the ground during drought, so that little more than the disc-like crown remains at the surface — the behaviour that gives it the name occulta, "hidden".
The body ranges from greyish-green through purplish to almost blackish, divided into low tubercled ribs, with modest, often dark spines that lie close to the surface rather than forming a showy armament; the spines tend to fall as the plant ages. Funnel-shaped flowers open from near the woolly crown, in whitish, yellowish to pale pinkish tones, followed by small reddish fruits. As with many dwarf Chilean species, individual plants vary considerably in body colour and spination.
Distribution and habitat
The species is native to the coastal fog desert of northern Chile, in the Taltal area of the Antofagasta region within the wider Atacama Desert. It grows in some of the driest terrain on Earth, rooting in gritty, mineral soils on open slopes and flats where much of the year's moisture arrives as coastal fog (camanchaca) rather than rain.
In these conditions the geophytic habit is a survival strategy: by shrinking into the ground behind its taproot, the plant conserves moisture and hides from both sun and grazing. Wild populations are localised and, like all cacti, the genus is listed under CITES; collecting from habitat is neither necessary nor appropriate when nursery-grown seedlings are available.
Cultivation
Like most Atacama dwarfs, Eriosyce occulta rewards a very lean regime and punishes excess water. Grow it in a deep pot to accommodate the taproot, in an extremely free-draining, mostly mineral mix, in bright light with only a little shielding from the fiercest summer sun.
Water sparingly during the growing period, always letting the mix dry out completely first, and keep the plant essentially dry through its long dormancy — cool, dry winters suit it well. The taproot is the plant's weak point in cultivation: standing moisture around the crown or roots leads quickly to rot. Good airflow and a gritty top-dressing help keep the neck dry. See Watering and Repotting for general technique.
Propagation
Seed is the standard and most reliable method. Sow onto a warm, mineral surface and keep humid until germination, then grow the seedlings on hard and lean to build a firm body and taproot. The species does not readily offset, so vegetative propagation is uncommon; vigorous growers sometimes graft seedlings to speed them along before returning them to their own roots. See Propagation — seed for a full walkthrough.
Common problems
- Rot — by far the commonest cause of loss, almost always from overwatering, a slow-draining mix, or moisture lingering at the crown or taproot.
- Etiolation — too little light makes the body soft, pale and elongated, losing its compact form.
- Pests — root mealybugs on the taproot and red spider mites on the body are the usual offenders; inspect the roots at repotting time.
See also
- Eriosyce — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — seed · Pests and diseases