Sulcorebutia rauschii
| Light | Very bright light; strong sun brings out the purple body colour |
|---|---|
| Water | Sparingly in growth; keep bone-dry through a cold winter rest |
| Soil | Gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Frost-tender in cultivation; give a cool, dry winter down to a few degrees above freezing |
| Propagation | Offsets (primary); seed; grafting to build up weak-rooted plants |
| Toxicity | Non-toxic to cats and dogs |
Sulcorebutia rauschii is a highly sought-after miniature cactus from the Bolivian highlands, prized for its small, flattened bodies that can range from lime-green to a deep, almost violet purple. Its tiny black spines are pressed flat against the body in neat comb-like rows (a pectinate arrangement), and in spring the little plants ring themselves with vivid magenta flowers that seem oversized for such a compact grower. It belongs to the genus Sulcorebutia, a group of small clumping cacti from the mountains of Bolivia.
Description
Sulcorebutia rauschii forms small, somewhat flattened globular stems only a few centimetres across, which in time offset from the base to build up a low cushion or clump. The body colour is famously variable: some clones stay a fresh lime-green, while others develop the intense purple to burgundy tones the species is best known for, with the strongest colour appearing on plants grown hard in bright light.
The spines are the other signature trait. They are short, dark and pectinate, lying flat against the ribs in tidy combs so that the plant reads as almost spineless from a distance. The stem is divided into low, spiralling ribs broken into small tubercles, each carrying a slender areole.
Flowers appear in spring, usually opening in a flush around the sides and base of the plant. They are a rich magenta to purple-pink, often with a paler throat, and are large in proportion to the tiny body, making a well-flowered clump a striking sight.
Distribution and habitat
The species is native to Bolivia, where it grows at high elevation in the mountains of the Andean region. Like other Sulcorebutia, it is found among rock and gritty mineral soils on slopes and outcrops, often tucked into crevices with sharp drainage and exposed to strong sun, cold nights and a pronounced dry season.
These montane conditions explain its cultivation needs: intense light, excellent drainage, and a genuinely cold, dry winter rest.
Cultivation
Sulcorebutia rauschii is not difficult given the right regime, and its small size makes it ideal for a windowsill or a spot in a bright greenhouse. Grow it in a very free-draining, mostly mineral mix and give it as much light as you can — this is what deepens the purple colouring and keeps the growth tight and characterful. Pale, elongated growth is a sign of too little light.
Water regularly but sparingly through the growing season, always letting the mix dry out fully between waterings, then keep the plant completely dry and cool over winter. This cold, dry rest is important both to encourage the spring flowers and to prevent rot. The species can be sensitive at the root, so many growers use a snug pot and take particular care with drainage; see Watering and Repotting for general technique. Weaker-rooted or slow individuals are sometimes grafted to build them up.
Propagation
Because the species clumps freely, the easiest method is to remove offsets and root them as offsets once any wound has calloused. It can also be raised from seed, sown on a warm mineral surface in the usual way (see Propagation — seed), which is the route to producing new colour forms. Grafting onto a vigorous rootstock is used both to speed up seedlings and to rescue plants with a troubled root system (see Grafting).
Common problems
- Rot — the commonest cause of loss, almost always from overwatering, a mix that holds too much moisture, or watering during the cold rest.
- Etiolation — too little light makes the body pale and swollen, and loses both the flat shape and the prized purple colour.
- Pests — mealybugs (including root mealybugs, so check the roots at repotting) and red spider mites are the usual offenders; see Pests and diseases.
See also
- Sulcorebutia — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — offsets · Propagation — seed · Repotting · Pests and diseases