Thelocactus hexaedrophorus
| Light | Bright light to full sun |
|---|---|
| Water | Sparingly; let the mix dry out fully between waterings, keep dry in winter |
| Soil | Gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 9–11, tolerates a light dry frost |
| Propagation | Seed (primary) |
| Toxicity | Non-toxic to cats and dogs |
Thelocactus hexaedrophorus is a low, solitary, flattened cactus from the arid highlands of northern and central Mexico, prized by collectors for its strongly geometric body and large, angular tubercles. Its blue-green to grey-green stem is broken up into distinct, chunky tubercles — the species name, meaning roughly "bearing six-sided bodies", refers to their almost faceted look — and in spring it opens broad, pale pink to white flowers from the crown. It is one of the more forgiving members of the genus Thelocactus and a good entry point into the group.
Description
Thelocactus hexaedrophorus usually stays solitary, forming a flattened globe that sits low and broad rather than tall. The body is firm and blue-green to greyish, divided not into continuous ribs but into large, separate, angular tubercles that give the plant its distinctive tiled, geometric surface. Each tubercle is tipped with an areole bearing a small cluster of stout radial spines and, often, one or a few longer central spines; spine length, colour and stiffness vary considerably from plant to plant and between habitat forms.
The flowers appear from the woolly crown in spring and early summer, funnel-shaped and fairly large for the size of the plant, in shades of pale pink to nearly white, sometimes with a darker midstripe or throat. They open in bright sunshine over the course of a few days.
Distribution and habitat
The species is native to the Chihuahuan Desert region of northern and central Mexico, across states such as Tamaulipas, Nuevo León and San Luis Potosí. It grows on limestone-derived soils in open desert scrub and grassland, frequently among rocks and low vegetation that give a little shelter. Across this range it is quite variable, and several regional forms, varieties and subspecies have been described on the basis of body colour and spination.
Like all cacti, Thelocactus is listed under CITES Appendix II, so international trade in wild-collected plants is regulated; nursery-grown seedlings are widely available and are the right way to obtain the plant.
Cultivation
T. hexaedrophorus is one of the easier Thelocactus to grow and is tolerant of a beginner's mistakes, though it still resents standing wet. Grow it in a very free-draining, mostly mineral mix in a pot that is not too deep, in bright light or full sun to keep the body compact and the spines strong. Water thoroughly once the mix has dried right through during the growing season, then let it dry again; keep the plant completely dry and cool through winter, which both prevents rot and encourages the following season's flowers. A hardy plant will take a light, dry frost, but reliable protection from freezing is safest. See Watering and Repotting for general technique.
Propagation
Seed is the standard and most reliable method. The seed germinates well on a warm, gritty surface kept humid until the seedlings establish, after which they are grown on hard and bright. Because the species almost always remains single and rarely offsets, vegetative propagation is uncommon; growers wanting to speed up young plants sometimes turn to grafting. See Propagation — seed for a full walkthrough.
Common problems
- Rot — the usual cause of loss, from overwatering, a slow-draining mix, or water sitting in the crown in cold conditions; the base or centre softens and discolours.
- Etiolation — too little light makes the body pale and pushes it to grow taller and softer, losing the flat, geometric outline and producing weak spines.
- Pests — mealybugs (white fluff in the areoles and on the roots) and red spider mites (fine webbing and a bronzed, dulled skin) are the most common; see Pests and diseases.
See also
- Thelocactus — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — seed · Repotting · Pests and diseases