Pediocactus sileri
| Light | Full sun; very bright light year-round |
|---|---|
| Water | Very sparingly; keep dry in summer heat and through a hard, dry winter rest |
| Soil | Extremely gritty, alkaline mineral mix, often with added gypsum (see Soil and potting mix) |
| Temperature | Cold-hardy; tolerates hard frost when bone-dry |
| Propagation | Seed (slow and challenging); often grown grafted |
| Toxicity | Non-toxic to cats and dogs |
Pediocactus sileri is a small, barrel-shaped cactus of the gypsum badlands of northern Arizona and southern Utah, and one of the more demanding members of the genus Pediocactus to keep in cultivation. It forms a low, ribbed body armed with stiff, pale spines and produces cup-shaped, dark-veined flowers of creamy to pale yellow. Known commonly as the Siler pincushion cactus, it is a federally protected species of the arid Colorado Plateau.
Description
Pediocactus sileri grows as a solitary (occasionally clustering) globe to short cylinder, usually only a few centimetres to around 15 cm tall and somewhat less across. The body is divided into low tubercles arranged in spiralling ribs, each areole bearing a dense cluster of spines. The central spines are stout and dark-tipped, ageing to a chalky grey or white, while finer radial spines fringe the areole — together giving the plant its bristly, pincushion-like look.
Flowers appear in spring from near the crown: broadly funnel-shaped and only a few centimetres across, with pale creamy-yellow to straw-coloured inner tepals marked by darker purplish or maroon midveins, the outer tepals often brownish and pale-margined. The small, dry fruits follow, splitting to release blackish seed.
Distribution and habitat
The species is restricted to a small area straddling the Arizona–Utah border, chiefly in the vicinity of the Vermilion Cliffs and the surrounding gypsiferous badlands. It grows on pale, gypsum-rich and alkaline clay soils in sparse desert scrub, where few other plants compete, typically among low shrubs at moderate elevations on the Colorado Plateau.
These are harsh sites — baking and dry in summer, cold in winter — and the plant is adapted to a specialised, mineral-poor substrate. Its narrow range and specific soil requirements are a large part of why wild populations are vulnerable.
Cultivation
Pediocactus sileri has a reputation as a difficult plant, and it is not a beginner's cactus. Its great weakness is intolerance of summer moisture around the roots: in habitat it does most of its growing in the cooler, moister parts of the year and rests through the heat. Grow it in a very open, almost entirely mineral mix — many growers add gypsum or limestone grit to raise alkalinity and mimic its native ground — in full sun with excellent airflow.
Water carefully in spring and autumn when the plant is in active growth, and keep it dry during the hottest weeks of summer and throughout winter. Although the species is cold-hardy when dry, wet cold is fatal. Because plants on their own roots are slow and rot-prone, many collectors grow P. sileri grafted onto a hardier rootstock, which sidesteps much of the root sensitivity. See Watering and Repotting for general technique.
Propagation
Seed is the usual method, though germination can be erratic and seedlings are slow and demanding. Sowing on a gritty, alkaline surface and giving the seed a cool, moist period often improves results, as it does for other Pediocactus. The species rarely offsets freely, so vegetative increase is uncommon except where growers root or graft the occasional pup. See Propagation — seed for a full walkthrough.
Common problems
- Rot — by far the biggest killer, almost always from summer watering, a mix that holds moisture, or wet cold in winter.
- Root loss on own roots — plants sulk or die back if the fine roots stay damp; grafting is a common insurance.
- Pests — root mealybugs in the dry mix and red spider mites in hot, still air are the usual offenders (see Pests and diseases).
Legal status
Pediocactus sileri is listed as threatened under the United States Endangered Species Act, reflecting its very limited range and vulnerability to habitat disturbance and illegal collection. Like all cacti, it is also covered by CITES, which regulates international trade in the family. Collecting plants or seed from the wild, and trading wild-taken material, is restricted by law.
These protections are about conservation, not psychoactivity: P. sileri is not a mescaline-containing cactus, and its listing has nothing to do with drug control. Nursery-propagated plants of documented cultivated origin are the responsible — and legal — way to grow the species. If you buy one, seek out reputable growers who can confirm their stock is seed-raised rather than wild-collected.
See also
- Pediocactus — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — seed · Pests and diseases