Epithelantha micromeris
| Light | Bright light; a little shade from the fiercest afternoon sun |
|---|---|
| Water | Sparingly; let the soil dry completely between waterings, dry rest in winter |
| Soil | Very gritty, mostly mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 9–11, tolerant of dry cold |
| Propagation | Seed (primary); offsets in clustering forms |
| Toxicity | Not known to be toxic to cats or dogs |
Epithelantha micromeris is a tiny globe-shaped cactus from northern Mexico and the southwestern United States, commonly known as the button cactus for its small size and neat, button-like shape. Its pale body is so densely clothed in minute, chalky-white spines that the green skin beneath is almost hidden, and mature plants produce tiny pink flowers at the very crown followed by slender, elongated red fruits. It is the best-known member of the genus Epithelantha.
Description
Epithelantha micromeris is a small, solitary or slowly clustering cactus, usually only 1–4 cm across, forming a flattened globe that may become shortly columnar with age. Rather than true ribs, the body is covered in tiny spiralling tubercles, each tipped with an areole bearing dozens of very short, fine white spines. These spines are so numerous and so tightly packed that the plant reads as a soft, powdery white button, and in many forms the spine tips at the crown are worn or shed to leave a felty apex.
The flowers are minute and easy to miss: pale pink to whitish, only a few millimetres across, opening right at the top of the plant from the woolly crown in spring and summer. They are followed by the feature many growers prize most — narrow, club-shaped fruits that ripen a bright red and stand up conspicuously above the white body, giving rise to the Spanish name chilitos ("little chillies").
Distribution and habitat
The species is widespread across the Chihuahuan Desert region, from Texas and New Mexico south into the Mexican states of Chihuahua, Coahuila, Durango, Nuevo León, Zacatecas and San Luis Potosí. It grows on limestone — in rock crevices, on gravelly slopes and desert flats — where it is often tucked among stones and nearly invisible until it flowers or fruits. Plants endure intense sun, sharp drainage and considerable seasonal drought and cold in habitat.
Because E. micromeris is variable across such a large range, botanists have described numerous local forms, varieties and related segregate species; hobbyists will encounter many names, but the plants intergrade and the boundaries are debated. Like the whole cactus family it is listed under CITES Appendix II, so nursery-propagated plants are legal to own and trade while wild collection is not.
Cultivation
The button cactus is a slow, undemanding plant that resents only one thing: excess moisture. Grow it in a very free-draining, mostly mineral mix in a small pot, in bright light with just a little shade from the harshest afternoon sun. Water thoroughly once the soil has dried out completely, then leave it be; keep the plant dry and cool through winter, which both prevents rot and encourages the following season's flowers. See Watering and Repotting for general technique.
Its natural limestone habitat means it appreciates a mineral, slightly alkaline substrate rather than a peaty one, and its fine white spination shows best when the plant is grown hard in strong light. Growth is genuinely slow, so plants stay small and pot-friendly for many years.
Propagation
Seed is the standard and most reliable method. The tiny seeds germinate on a warm, humid mineral surface and seedlings are raised on much as for other small desert cacti — see Propagation — seed. Clustering forms can also be increased by removing rooted offsets once they have formed their own base (see Propagation — offsets), though the solitary forms rarely offer this option. Because seedlings are slow, some growers graft young plants onto a vigorous rootstock to speed them along before growing them on their own roots.
Common problems
- Rot — by far the commonest cause of loss, from overwatering, a slow-draining mix or moisture sitting on the crown; the plant softens and discolours from the base.
- Etiolation — too little light makes the body stretch and lose its tidy button shape and dense white spination.
- Pests — mealybugs (white fluff hiding among the spines, easy to overlook here) and red spider mites are the usual offenders; see Pests and diseases.
See also
- Epithelantha — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — seed · Propagation — offsets