Epithelantha, commonly known as button cactus, is a small genus in the family Cactaceae (order Caryophyllales) comprising eight accepted species of miniature cacti native to the Chihuahuan Desert region of north-eastern Mexico and the south-western United States, ranging from western Texas to Arizona.
Plants in this genus are among the smallest cacti, forming globe-shaped to shortly cylindrical stems typically no wider than about 2.5 cm (1 inch) in diameter. The stem surface is densely covered by numerous tiny, whitish spines arranged around the tubercles, giving the plants a soft, button-like or powdery appearance that accounts for their common name. Flowers are correspondingly minute and emerge from the very tip of the stem, near the apex of the tubercles — a placement that is the literal source of the genus name. Fruits are slender and bright red when ripe, and all species are reported to bear edible fruits.
The genus was described with the type species Epithelantha micromeris, a low-growing cactus found on limestone outcrops and gravelly desert soils. The group is popular among cactus collectors owing to its compact size and the contrast between the densely spiny, muted stems and the vivid red fruits.
Etymology
The genus name Epithelantha is derived from Greek: epi (upon), thele (nipple or tubercle), and anthos (flower), referring to the distinctive position of the flowers at the very apex of the tubercles.
Distribution
Epithelantha is native to the Chihuahuan Desert region, occurring in north-eastern Mexico and the south-western United States from western Texas to Arizona. Plants typically grow on rocky limestone hillsides and gravelly desert soils at various elevations within this arid zone.
Cultivation
Button cacti are popular among miniature-cactus collectors. They require very well-drained, gritty or mineral-rich substrate, full sun, and minimal watering — particularly during winter dormancy. Their small size makes them well suited to container growing. Temperatures should not remain freezing for extended periods, though brief cold spells are generally tolerated.
