Turbinicarpus valdezianus
| Light | Bright light with a little shade from the fiercest summer sun |
|---|---|
| Water | Very sparingly; dry fully between waterings, keep bone-dry in winter |
| Soil | Gritty, sharply draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; cool, dry winter rest; roughly USDA zones 9b–11 |
| Propagation | Seed (primary); grafting to speed slow seedlings |
| Toxicity | Not known to be toxic to cats or dogs (no specific data); the fine spines are the main hazard |
Turbinicarpus valdezianus is a tiny, globular cactus from the Chihuahuan Desert of northern Mexico, prized for the soft, feathery white pectinate spines that clothe its little body and for the disproportionately large violet-pink flowers it throws in late winter. Rarely more than a couple of centimetres wide, it is one of the smallest and most charming members of the genus Turbinicarpus, and has long been shuffled between related genera — you will still see it sold under the synonyms Pelecyphora valdeziana, Gymnocactus valdezianus and Normanbokea valdeziana.
Description
Turbinicarpus valdezianus forms a small, solitary (occasionally clustering) body seldom more than about 2 cm across, sitting atop a stout, contractile taproot that pulls the plant down into the soil during drought. The body is built from tiny spiralled tubercles, each tipped with an areole bearing many short, soft, comb-like (pectinate) spines. These spines are chalky white and lie flat against the surface, overlapping into a felted, feathery covering that all but hides the green skin beneath.
The flowers are the plant's great surprise: emerging from the woolly crown, they are violet-pink to magenta with a paler throat and darker midveins and, at up to about 2 cm across, can be nearly as wide as the whole plant. They open in the cooler months — typically late winter into early spring — for a few days at a time in bright light.
Distribution and habitat
The species is endemic to Mexico, restricted to a limited area in the states of Coahuila and San Luis Potosí — roughly from Saltillo south to near Matehuala, at around 1,400–1,600 m — where it grows in Chihuahuan Desert scrub. Plants tuck themselves into gritty, limestone-derived soils among rocks and low vegetation, often sitting almost flush with the ground so that only the spiny top and occasional flowers give them away.
Like the rest of the genus, T. valdezianus has a naturally small range and is sought after by collectors, which puts pressure on wild plants. The entire genus Turbinicarpus is listed under CITES Appendix I, the strictest level of international trade protection. Nursery-propagated, seed-grown plants are widely available, legal to own and trade, and should always be preferred; collecting or buying wild-dug plants is both harmful and illegal.
Cultivation
This is a small, slow, taprooted cactus that rewards restraint. Grow it in a deep, snug pot to accommodate the taproot, in a very free-draining, mostly mineral mix with plenty of grit, and give it bright light with only light shading from the most intense summer sun — good light keeps the spine cover dense and the body compact. Water thoroughly only once the soil has dried right out, and then wait; err firmly on the side of underwatering, as the fleshy taproot rots easily in cold, damp conditions.
Through winter keep the plant completely dry and cool. This dry rest hardens the plant, helps prevent rot and is what triggers the early flowers. See Watering and Repotting for general technique.
Propagation
Seed is the standard and most reliable method. The fine seed germinates on a warm, damp mineral surface and, though seedlings are slow, they grow into strong plants on their own roots. Because the species offsets only occasionally, vegetative propagation is uncommon. Many growers graft young seedlings onto a vigorous rootstock to push them past the vulnerable early stage more quickly, then may root the grown plant down onto its own roots later. See Propagation — seed for a full walkthrough.
Common problems
- Rot — by far the commonest cause of loss, almost always from overwatering, a slow mix, or cold damp conditions reaching the taproot; the plant softens and discolours, often from the base.
- Sparse, weak spination — too little light produces a soft, etiolated body with a thin, open spine cover instead of the dense white felt.
- Pests — root mealybugs on the taproot (check when repotting) and red spider mites are the usual offenders; see Pests and diseases.
See also
- Turbinicarpus — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — seed · Repotting
- CITES — international trade protection