Epithelantha (2018)

By Jolie Krupnik (March 2018)

What compels us to purchase a cactus? Or better yet, what features of the cactus draw us in and excite us to want to learn more about the species or genus?

Is it a circling pattern of pale flowers, or big flowers with bright colors? Maybe it is the color, shape or perhaps hairy texture of its spines. Or is it the pattern of tubercles that swirl around the stem? Maybe it is nothing more than the challenge of growing a difficult specimen.

For me, I saw photos of a flowering Epithelantha greggii, and I fell in love.

Looking at photos, the relative size of the plant is not evident, but epithelanthas are very small – one of the smallest plants in the Cactaceae family. Mature stems, on average, measure no more than a few inches in diameter and at their largest height, grow to no more than 4 inches.

Examples of the tallest growers are E. greggii ssp. greggii, E. unguispina ssp. unguispina and E. pachyrhiza ssp. elongata. E. micromeris and E. pachyrhiza ssp. parvule are among the smallest species in this genus, the latter growing to no more than an inch wide.

The flowers on epithelanthas also are small, appearing on the aureoles on a woolly apex of the stem. The flowers on E. greggii are a soft pinkish-white color and campanulate, or bell-shaped. All epithelantha flowers are bell-shaped, but their colors can vary from white or pink to orange and gray.

The most commonly known and available Epithelantha species in cultivation is E. micromeris. There are several reasons for this. First, it has the widest distribution area, ranging from the southwestern United States down to the Coahuila and Nuevo Leon states in Mexico.

Second, it is the only species in this genus that is automagous, or self-fertile. All other Epithelantha species are self-sterile and must be cross-pollinated. According to Miles Anderson, owner of the mail order website Miles’ To Go, with the exception of E. micromeris, he has to hand pollinate epithelanthas from plant to plant to get seed. “E. micromeris doesn’t require anything and sets fruits on its own,” he said.

The scarlet-red fruit of epithelanthas is one of their most striking features, attracting birds and small mammals that digest and disperse the seeds, and contribute to the survival of the genus. The contrast of the red fruit against what looks like a blanket of white is dazzling; Epithelanthas have such dense white spination that the green epidermis underneath can barely be seen.

The etymology of Epithelantha derives from three Greek words: “epi” – meaning over, or on top; “thele” – meaning nipple; and “anthos” – meaning flower. Thus, the genus name means “plant with flowers on the nipples (tubercles).” The common name in the U.S. is button cactus.

According to Davide Donati and Carlo Zanovello, authors of the monograph Epithelantha 2011, the name Epithelantha was chosen (though no date is given) to remove the plants from the Mammillaria genus. In 1856, the botanist George Englemann had originally classified epithelanthas as mammillarias.

While epithelanthas look quite similar to mammillarias, the distinction is in the flowers. The flowers of Epithelantha develop on the apex areoles, while the flowers of Mammillaria develop on the axils, the area between the tubercles, in a circle around the stem.

In their natural habitat, epithelanthas grow in crevices and small depressions on limestone in arid areas under full sun. In cultivation, great care must be given to use a well-draining soil and water sparingly, as epithelanthas are prone to root rot with too much water. Full sun is also needed to prevent elongation. Fertilizer also should be used sparingly.

In a Web search, you will most likely find only two species under the genus Epithelantha – E. micromeris and E. bokei – and will read that all epithelanthas look alike. But don’t be led astray.

Only these two species are found in natural habitat in the United States and Mexico. Other variations of these plants, found only in Mexico, were classified over the years as one of these two species or as subspecies. In 2010, however, after years of field and lab research, Donati and Zanovello identified “12 different taxa, six of which recognized at specific level.” (In their list, I counted 13 taxa with seven at the specific level. Possibly the translation from Italian to English is causing the confusion.)

The “specific levels” they identified, which I interpret to mean species, are E. micromeris, E. bokei, E. ilariae, E. greggii, E. unguispina, E. pachyrhiza and the newest species, E. cryptica. In part, their findings were based on the fact that these different species with distinct spination and other separate characteristics cohabited, and no hybrids were found.

Would you like to own an E. micromeris? I will have several for sale at the March meeting. The price is $5 each. They are single-stemmed with fruit and are 3 to 4 years old.

Sources:
Epithelantha 2011, by Davide Donati and Carlo Zanovello – Published by The Cactus Trentino Südtirol Society
CactiGuide.com – http://cactiguide.com/cactus/?genus=epithelantha
Epithelantha, by Pam Schnebelen – HSCSS Digest, October 2006
Miles Anderson, owner of the mail order website Miles’ To Go
Don Lesmeister, HSCSS member