Strombocactus corregidorae
| Light | Bright light; a little shade from the fiercest afternoon sun |
|---|---|
| Water | Very sparingly; allow to dry completely between waterings, dry rest in winter |
| Soil | Extremely free-draining, mostly mineral mix (see Soil and potting mix) |
| Temperature | Keep frost-free; tolerates cool, dry winters |
| Propagation | Seed |
| Toxicity | Non-toxic to cats and dogs |
Strombocactus corregidorae is a slow-growing, spiny cactus from central Mexico, described in 2010 as the second species in the genus Strombocactus. It is closely related to the long-familiar Strombocactus disciformis, but is set apart by its larger, more robust, eventually elongated body and its well-developed, persistent spines — rather than the flattened, almost spineless disc of its cousin — and by its restricted home along the canyon of the Río Moctezuma.
Description
Strombocactus corregidorae is the most robust member of its genus. Young plants are globose-depressed to top-shaped (turbinate), while mature plants become globose to elongated-cylindrical, reaching roughly 18–23 cm tall and 8–12 cm across, greyish-green to glaucous. The body is divided into spiralled, tile-like tubercles that give the surface a characteristic tessellated, artichoke-like pattern.
Unlike the nearly naked Strombocactus disciformis, the areoles carry well-developed spines: the upper ones shorter and more flexible, the central and lower ones longer (to about 2–3.5 cm), rigid and persistent, grey when young and ageing to grey-black, so that spines clothe much of the body. This spination, together with the larger, more elongated habit, is the most reliable way to tell the two species apart.
The flowers open from the crown, are funnel-shaped and yellow, and measure about 3.5–4 cm long and wide — broadly similar to the whitish, cream or pale-yellow flowers of S. disciformis, so flower colour is not a dependable diagnostic. As in the whole genus, the seeds are very small, a detail that matters when it comes to propagation.
Distribution and habitat
The species is a narrow endemic of central Mexico, known from the canyon system of the Río Moctezuma (the Infiernillo canyon), on the borders of the states of Querétaro and Hidalgo. It grows lodged in crevices and on steep, rocky faces of vertical or near-vertical canyon walls, at around 1,500 m in desert and dry scrub, rooting into thin mineral pockets.
Because its range is so limited, S. corregidorae is of conservation concern, and — like the whole genus Strombocactus — is listed on CITES Appendix I, the strictest category, so that international trade is tightly restricted. Wild plants should never be collected; seed-raised, nursery-propagated material is the only responsible way to grow it.
Cultivation
This is a slow, specialist plant that rewards patience and a very cautious hand with water. Grow it much as you would Strombocactus disciformis: in an extremely free-draining, largely mineral mix, in a deep pot that accommodates the root, and in bright light with only light shading at the hottest part of the day. Water thoroughly but infrequently during the growing season, always letting the mix dry out completely first, and keep the plant dry and cool through winter to prevent rot and encourage flowering.
Overwatering and a soil that holds moisture are the quickest ways to lose a plant. Many growers keep the base a little proud of the surface and top-dress with grit to keep moisture away from the neck. See Watering and Repotting for general technique. Because seedlings are so slow, some growers graft them to speed early growth before returning them to their own roots.
Propagation
Seed is effectively the only method. The seeds are minute, so they are surface-sown onto a fine, firm mineral surface, kept warm, humid and brightly lit, and never buried. Germination can be erratic and the seedlings are tiny and slow, needing careful, gentle moisture management for the first year or two. The species does not offset freely, so vegetative propagation is largely limited to grafting. See Propagation — seed for a full walkthrough.
Common problems
- Rot — by far the commonest killer, almost always from overwatering, a moisture-retentive mix, or water sitting around the neck; the body softens and discolours from the base.
- Root rot — a pot that stays wet, or careless winter watering, can rot the thickened root even when the top still looks healthy.
- Etiolation — too little light makes the body pale, soften and grow abnormally, losing its natural form.
- Pests — mealybugs (white fluff in the tubercle grooves and on the roots) and red spider mites are the usual offenders.
See also
- Strombocactus — the genus overview
- Strombocactus disciformis — the closely related type species
- Grafting · Soil and potting mix · Watering · Propagation — seed · Repotting