Sulcorebutia steinbachii
| Light | Bright light with some direct sun; a little shade from the fiercest afternoon heat |
|---|---|
| Water | Regularly in the growing season once the mix has dried; keep dry and cool in winter |
| Soil | Gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; USDA zones 9–11 (tolerates a brief, dry cold snap) |
| Propagation | Offsets (easy); also seed |
| Toxicity | Non-toxic to cats and dogs |
Sulcorebutia steinbachii is a small, clustering cactus from the Bolivian Andes and one of the most widespread and variable members of its genus. It forms tight cushions of low, globular heads, and across its many regional forms the spring flowers range through red, purple-magenta, orange and yellow — a colour spread unusual for a single species and a large part of why collectors prize it.
Description
Sulcorebutia steinbachii produces small green to purplish-green stems, each usually only a few centimetres across, that cluster freely into low mounds with age. The body is divided into spiralling, tuberculed ribs, and the elongated ("sulcate") areoles that give the genus its name run as narrow grooves along the top of each tubercle. Spines are typically short, comb-like (pectinate) and pressed close against the body, varying from pale to dark brown between forms.
The flowers are the main event: funnel-shaped blooms, roughly 2–4 cm across, that open around the sides of the plant in spring. Depending on the form and provenance they may be deep red, magenta-purple, orange or clear yellow, and a well-grown clump in full flower can nearly hide its own stems.
Because the species is so variable, many local populations have at one time carried their own names (as separate species, subspecies or varieties). Modern treatments fold most of these into a broad, polymorphic S. steinbachii, but the old names still circulate widely on collection labels.
Distribution and habitat
The species is native to the mountains of central Bolivia, chiefly in the Cochabamba region, where it grows at moderate to high elevation on rocky slopes and in gritty, well-drained ground among grasses and low vegetation. Plants there experience strong sun, a distinct summer rainy season and a cold, dry winter — the pattern their cultivation aims to imitate.
Like the whole cactus family, Sulcorebutia is listed under CITES Appendix II, which governs international trade. Nursery-raised plants are widely available and entirely legal to own and trade; wild collection is not.
Cultivation
Sulcorebutia steinbachii is one of the easier and more forgiving of the small Andean cacti, which makes it a good starting point in the genus. Grow it in a gritty, mostly mineral mix in a pot with ample drainage, in bright light with a few hours of direct sun to keep the growth compact and encourage flowering. Water moderately through the warm growing months once the mix has dried, then taper off.
A cold, completely dry winter rest is the single most important step for good flowering: kept dry, the plant tolerates surprisingly low temperatures, but wet cold quickly causes rot. As with most highland cacti, the fat, water-storing roots resent sitting damp, so err toward underwatering and see Watering and Repotting for general technique.
Propagation
The species offsets readily, so the simplest method is to detach a rooted or unrooted head, let any cut surface callus, and pot it up — see Propagation — offsets and Propagation — cuttings. It also grows well from seed, which is the route to preserve the range of flower colours and forms; sow on a warm, gritty surface kept humid until germination, as described in Propagation — seed. Vigorous or slow clones are sometimes grafted to speed them along, though this species rarely needs it.
Common problems
- Rot — the usual killer, almost always from watering while cold or from a mix that holds moisture; heads soften and discolour from the base.
- Failure to flower — generally too little light or the lack of a dry winter rest.
- Etiolation — insufficient sun makes the stems pale and elongate, loosening the tidy cushion shape.
- Pests — mealybugs (including root mealybugs on the thick roots) and red spider mites are the ones to watch; see Pests and diseases.
See also
- Sulcorebutia — the genus overview
- Soil and potting mix · Watering · Repotting
- Propagation — offsets · Propagation — seed · Grafting