The flowers are generally whitish pink in color and are quite small. Oftentimes, one fails to see the small flowers amid the thick spination of the plants. Most of these Living Buttons eventually cluster to form small to mid-sized clumps, although one or two may stay solitary for some time. I have some plants that have over 20 heads under an inch in diameter each. I have, however, seen fantastic clumps in Japan of some of the varieties with well over a hundred heads!
Epithelanthas bear the closest resemblance to mammillarias, as both are heavily tubercled plants. These differ in the location of their flowers. Whereas in mammillarias the flowers arise from the axils (the areas between the tubercles), in epithelanthas they emerge from the newest areoles on the crown. Epithelanthas generally are also much smaller growing than the mams. Some botanists believe there is only one species, E. micromeris, with a number of distinct varieties. Others believe there are several distinct species, differentiated not just by the difference in the spine formations but also in terms of the forms of the roots as well as habitat habits. For simplicity’s sake, I am going to describe this genus in the context of the latter belief.
E. micromeris is the type plant and attains a size of between two and five cm. in diameter per head, becoming more elongated in age and clustering to form densely packed clumps of small stems to about five to six inches across. Each areole bears between 20 and 30 mostly white marginal spines. Like the other species in this genus, E. micromeris is found growing in very sunny locations, usually on calcareous knolls as well as in dry riverbeds. There is one recognized form, forma neomexicana from New Mexico. It differs from the type by having slightly different spine formations, but is altogether quite similar to the type.
E. micromeris v. greggii is probably the closest-looking to the type plant. It is the only variety I will maintain in this discussion. Variety greggii grows a bit larger than micromeris, up to five to six cm. in diameter per head. It produces numerous offshoots and forms huge clumps. Its spines stick out from the stem in every direction (as opposed to the type plant’s more uniform spine formations) and the spines are variable in coloration, from white to brownish pink.
The most beautiful and coveted species for me is E. bokei. Unlike micromeris, this plant has the most number of spines per areole in the genus, up to 40. This gives the plant a beautiful milky white to cream appearance. Smaller plants really look like cream-white buttons. My plants are from the southern Texas region, with some growing in limestone formations similar to Ariocarpus fissuratus.
E. pachyrhiza differs from the type in that it has a more elongated, club-shaped growth to its stem. It also possesses a thick, tuberous, turnip-like root. It attains a diameter of three to four cm., but can grow several inches in height. It usually stays solitary for some time before producing a mass of offsets later in life. While very careful watering is in order for all the button species, extra care is required for E. pachyrhiza given its tuberous root which is more sensitive to overwatering.
E. polycephala is a columnar-stemmed, heavily clustering variety, with the stems reaching about two to three cm. in diameter and up to six cm. or so in height. Spines are white with orange brown tips, quite dense, and do not lie flat to the body. In my book, this species looks totally different from the type plant.
E. unguispina is sometimes classified as a variety of E. bokei. It is, for me anyway, the easiest and most robust growing species in the genus. It has globular stems three to five cm. in diameter, clustering heavily around the base and characterized by black-tipped central spines. The new growth of mature plants is oftentimes topped with thick white wool, a major attraction of this species. It is best not to water these plants from the top so that the beautiful wool is not washed away. Unfortunately for me, some of my plants fail to continue to produce this white wool in our hot and humid climate.
The newest species to be described is E. dickisoniae. In appearance it shows most affinity with E. polycephala. Both are columnar growers with narrower stems, and both eventually produce numerous offsets. The coloration of the spines is quite different, with E. dickisoniae having lighter colored spines. All of the offsets produced by my E. dickisoniae plants come from the middle of the parent stems, not from the base of the plants like in the type plant.
Epithelanthas are again not the easiest of cacti to grow well, particularly in tropical climates like ours. I would say their treatment should be similar to that for ariocarpus. The first thing to remember is that these are quite slow-growing plants. I try to give my Buttons as much direct sunlight as possible, given the limitations of my greenhouse location. Strong sunlight is essential to keeping the plants growing compactly. Essentially, the growing medium should be mineral in content, with little to no organic materials added. The substrate should be very porous, allowing excess water to drain from the pot hole. Based on this principle, I use 1/3 good sandy garden loam (which is getting harder and harder to find these days), 1/3 perlite which loosens and airs the soil, and 1/3 gravel and crushed brick.
Whether growing the plants in clay or plastic pots, always water only when the growing medium has thoroughly dried out, never when this is still wet or moist. Since I grow my plants in plastic pots, this means watering once a week during the epithelanthas’ growing period from around March to September, and once every two or three weeks the rest of the year. I only fertilize during the plant’s growing period, generally using a very diluted mix every other watering. I don’t fertilize after September, and not before March. I used to fertilize these plants every time I watered during the growing season, but some of the plants started to elongate, grow flabby, lose their compactness and the overall growth was altogether not true to form. For this plant, we should always be mindful that it is a slow grower and should not be forced in any way.
Very few pests attack epithelanthas if the plants are sturdy and grown well. If ever, the key threat would be root mealy bugs which attack and suck the juices from the roots. However, watering once or twice a year with water containing some diluted insecticide like malathion mixed in should be a good practice. Epithelanthas are quite difficult to flower in my growing conditions in Metro Manila. Again, these require cooler nights just like ariocarpus. However, I grow the plants for their beautiful spination and cute forms. The challenge, then, is to try to grow these plants as true to form as possible, and believe me, this is enough of a challenge with these Living Buttons.