Turbinicarpus laui
| Light | Bright light with a little shade from the harshest afternoon sun |
|---|---|
| Water | Very sparingly; allow to dry out completely between waterings, and keep bone-dry through winter |
| Soil | Gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep frost-free; hardy to light frost only if kept dry, roughly USDA zones 9b–11 |
| Propagation | Seed (primary); occasional offsets from older plants |
| Toxicity | Non-toxic to cats and dogs |
Turbinicarpus laui is a miniature, slow-growing cactus from north-central Mexico and a member of the genus Turbinicarpus. Its little grey-green heads carry slender, glassy-white spines, the uppermost curving in over the crown, and it opens small, funnel-shaped flowers in white to pale pink. Plants are usually solitary, sometimes forming a small cluster with age.
Description
Turbinicarpus laui is a small species, the single body reaching only about 3.5 cm across and a centimetre or so tall, sub-globose to somewhat flattened. It is usually solitary but may offset slowly to build up a small cluster with age. The greyish-green body is divided into low tubercles rather than sharp ribs.
The spines are slender and needle-like, glassy white and often darker at the tip, spreading and radiating from the areoles; the uppermost are longer and curve inward, meeting over the crown. They are relatively fine but firm — not the soft, pectinate combs of some of its close relatives. Small, funnel-shaped flowers appear from the crown, white to pale pink with a slightly darker midstripe, and are fairly large in proportion to the little body.
Distribution and habitat
Like most of the genus, T. laui is endemic to the arid country of north-central Mexico, where it is restricted to a small area of gypsum and limestone hills in the state of San Luis Potosí. Plants root in gritty, mineral soils and rocky crevices, often tucked among stones or low vegetation that gives a little shade and shelter. In the wild the small, cryptically coloured bodies can contract down into the substrate during drought, making them very hard to spot.
Wild populations are small and localised, and the species is assessed as Critically Endangered; the entire genus Turbinicarpus is listed under CITES Appendix I, the strictest level of protection, reflecting the pressure that illegal collection has put on these miniatures. Nursery-propagated, seed-grown plants are widely available and entirely legal to own and trade; collecting from habitat is not.
Cultivation
Turbinicarpus laui is a rewarding little plant for the collector who can resist overwatering, which is by far the commonest cause of loss. Grow it in a very free-draining, largely mineral mix in a small pot, in bright light with just a little protection from the fiercest summer sun. Water thoroughly only when the soil has dried out completely, then allow it to dry again; keep the plant completely dry and cool through winter to prevent rot and to encourage spring flowering.
Because the plant has a thickened root and dislikes staying wet, careful Watering and occasional Repotting into fresh gritty medium go a long way. Growth is slow but steady, and a well-grown plant is charming out of all proportion to its size.
Propagation
Seed is the standard and most reliable method. The fine seed germinates readily when sown on a warm, mineral surface kept humid, and seed-raising is how most collection plants are produced. Older plants may occasionally produce an offset, which can be detached once it has its own roots, or teased off and set to callus before potting; see Propagation — offsets and Propagation — seed for full technique. Some growers graft seedlings onto a vigorous rootstock to bulk them up quickly before growing them on their own roots.
Common problems
- Rot — almost always from overwatering, a slow-draining mix, or water sitting in the crown; the plant softens and browns, often from the root up.
- Etiolation — too little light makes the small body stretch and pale, spoiling its tight symmetry.
- Pests — root mealybugs hidden in the rootball are the classic threat to potted plants; spider mites and above-ground mealybugs also occur. See Pests and diseases.
See also
- Turbinicarpus — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — seed · Propagation — offsets