Epithelantha
Epithelantha is a small genus of diminutive cacti in the family Cactaceae, native to the deserts of the southwestern United States and northern Mexico. Commonly known as button cacti, these plants form tidy little globes or clusters so densely clothed in tiny, chalk-white spines that the green body beneath is all but hidden. Mature plants bear small pink-tinged flowers at their crown, followed by the genus's signature bright red, club-shaped fruits that stand out like little beads against the white wool.
Description
Epithelantha plants are among the smaller cacti in cultivation, most forming solitary or clustering globes only a few centimetres across, though the largest species can build up into low mounds over many years. The body is divided into numerous tiny, spiralling tubercles rather than distinct ribs, and each tubercle is tipped with an areole bearing many minute, appressed white spines. In most species these spines are so short and so densely overlapping that the whole plant takes on a smooth, felted, snow-white appearance — a look that gives the genus much of its charm.
The small flowers open near the growing point at the top of the plant, typically pale pink to whitish, and are modest compared with the showy blooms of many other cacti. The fruits, however, are distinctive: elongated, club- or finger-shaped and vivid red, they ripen at the crown and are often the most eye-catching feature of a plant. These red fruits are thought to attract birds, which help disperse the tiny seeds.
Distribution
The genus is centred on the Chihuahuan Desert and adjacent arid regions, ranging from western Texas, southern New Mexico and neighbouring parts of the southwestern United States down through the northern and central Mexican highlands. Plants are typically found on limestone outcrops, rocky slopes and gravelly flats, often growing tucked among rocks or nestled into crevices where a little extra shelter and drainage are available. In habitat they are easily overlooked, blending into pale rock and sitting low to the ground.
Notable species
- Epithelantha micromeris — the classic and most widely grown button cactus, a small white globe and the type species of the genus.
- Epithelantha bokei — prized for its exceptionally smooth, dense white spination that gives an almost polished, poreless look.
- Epithelantha pachyrhiza — a species notable for its thickened, tuberous root.
- Epithelantha micromeris var. greggii — a larger, more freely clustering form associated with parts of northern Mexico.
The number of recognised species and varieties has shifted with revisions over the years, and several taxa are treated by some authors as varieties of E. micromeris rather than as species in their own right.
Cultivation
Button cacti are rewarding for growers who enjoy small, slow, jewel-like plants, but they demand the same care with water that suits most desert cacti. Grow them in a very free-draining, mostly mineral mix with plenty of grit, ideally with added limestone or crushed rock to reflect their native substrates. Give them bright light, which keeps the spination tight and white and the body compact; too little light causes weak, etiolated growth.
Water sparingly during the warm growing season, always allowing the soil to dry completely between waterings, and keep the plants dry and cool through winter to prevent rot and encourage flowering. Their small size and fine roots make them sensitive to sitting in wet soil, so a snug pot and careful Watering go a long way. Because they are naturally slow, some growers graft young plants onto a vigorous rootstock to speed them along, though many are grown perfectly well on their own roots with patience. See Repotting for general technique.
Propagation
Most Epithelantha are grown from seed, which germinates readily on a warm, gritty surface kept lightly humid. Clustering species and forms can also be increased by carefully removing rooted offsets from the clump (see Propagation — offsets). Grafting is sometimes used to grow on slow or delicate seedlings more quickly.
Hobby notes
Button cacti are popular with collectors of miniature and windowsill cacti, where their neat proportions and bright fruits make them favourites in small pots and dish arrangements. Epithelantha bokei in particular is sought after for its flawlessly smooth white surface, and several crested and clustering forms circulate among enthusiasts. As with all cacti, the genus is listed under CITES Appendix II; nursery-propagated plants are widely and legally available, while collecting from the wild is discouraged and often illegal.
See also
- Cactaceae — the cactus family
- Soil and potting mix · Watering · Grafting · Propagation — seed · Propagation — offsets · Pests and diseases