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Along with other articles, columns and club updates, each monthly issue of the Henry Shaw Cactus Digest includes an article or two on members' favorite cactus and succulent species. The articles typically include photos and facts on the plants' natural origins and distribution, growing conditions, common and scientific names, care and cultivation tips, and helpful hints for encouraging flower production.
Follow the links below this month's offering(s) to enjoy previous Plants of the Month or click to read a sample of the HSCSS Digest in PDF format.
March 2018 -- Epithelantha
By Jolie Krupnik
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.
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
March 2018 -- Trichodiadema
By Bob Williams
The genus Trichodiadema is a member of the Aizoaceae family. Some members of this large and diverse family include Aloinopsis, Conophyllum, Delosperma, Lithops, Mesembryanthemum, Nananthus, Rabia and Titanopsis. Just looking at a few of the plants in these genera reveals a few things about Trichodiadema.
First, they do not grow very tall. The maximum height for the largest Trichodiadema species is 12 inches. Most are in the 3- to 6-inch range.
Second, these plants grow low to the ground and spread out. The largest Trichodiadema species have diameters up to 12 inches when fully grown. Most are half that size.
For the home brewers and cooks in the crowd, this plant group is for you. Roots of some species of Trichodiadema have been used in the past to speed the fermentation of bread, beer, etc. The roots contain yeast or sugars that increase the rate of fermentation.
The name Trichodiadema comes from the ancient Greek "trikhos," meaning hair or bristle, and "diadema," meaning crown. The genus Trichodiadema, comprised of around 30 species, is found in southern Namibia and in the Northern, Western and Eastern Cape Provinces in South Africa.
By looking at where these plant grow, we know that high heat, bright sun and sparse rainfall are the norm. We also know that in order for them to survive, water will be stored in the roots -- creating a good-looking caudex.
Trichodiadema bulbosum grows in the Western and Eastern Cape regions of South Africa. This is also described as the Port Elizabeth region. In 1814, this plant was given the name Mesembryanthemum bulbosum by Adrian Hardy Haworth. It was given the name Trichodiadema bulbosum by Martin Heinrich Gustav Schwantes in 1926. This is the currently accepted name.
T. bulbosum is one of the larger plants in the genus, growing to a height of 12 inches and branching out to a diameter of 12 inches. The leaves are many but small, with each leaf about one-eighth inch wide and no more than one-half inch long. The leaves have a light waxy coating. For these plants, water conservation is key.
This plant has attractive flowers that range from violet to purple red with a yellow center. In comparison to the size of the leaves, the flowers are very large. Flowers can be from 1 1/2 to 2 1/2 inches in diameter. Even if you don't want to grow T. bulbosum for the caudex, grow it for the flowers. Another plus: This plant will flower all summer long, from late spring to early fall.
Trichodiadema bulbosum is a popular bonsai plant among bonsai enthusiasts. Over time, the caudex will expand to the diameter of the plant. This means if I do everything right, and the plant likes me, I could have a twisted, knotty caudex in the 8- to 12-inch-diameter range.
Care for the plant should reflect the basic care practices for other plants found in the hot and dry regions of Western Africa. The soil mix should drain well and contain some grit. Care information from some sources suggested that a soil mix with a small amount -- no more than 10 percent -- of organic matter works best.
T. bulbosum should be watered well during the growing season. Every source said to not let the soil mix dry out during this period. The plant can tolerate high heat and bright, direct sunlight. Some sources said better growth can be attained by giving the plant direct morning and afternoon sun, but bright indirect sun during the heat of the day. I am not sure how you do that. This plant can take a light frost, but is not cold-hardy in our area.
It is fairly easy to find these plants for sale on the Web. You may also find them at your local Walmart under the common name of "ice plant."
Note: As announced in January, Bob Williams is embarking on an experiment to see if pot size affects caudex growth. He will raise plants of the same species and size under the same conditions for three growing seasons, but vary pot size. Trichodiadema bulbosum is the first test species. The plants' caudices will be compared in the spring of 2021.
Succulent Gardening -- http://www.succulents.us/trichod.html
LLifle Encyclopedia of Succulents -- http://www.llifle.com/Encyclopedia/SUCCULENTS/Family/Aizoaceae/
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