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PLANT OF THE MONTH

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.

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February 2019 -- Mammillaria bertholdii

By Pat Mahon
 
Since many of the larger cacti have already been discovered, there are plenty of diminutive species still hiding away. One of these happens to be a gorgeous new Mammillaria species with a growing habit simlar to that of Ariocarpus. This new species does not resemble rocks and gravel though, but instead looks like a cluster of perfect eyelashes.
 
A remarkable find in the cactus world, Mammillaria bertholdii was only recently discovered in 2013 by Andreas Berthold in Oaxaca, Mexico. This is one of the laughably disproportionate cacti, in which the flower and the tuberous root system are generally much larger than the entire plant!
 
The elevation and topography of M. bertholdii's habitat in Oaxaca are quite variable. Much of Oaxaca is diverse, leading to a surplus of unique and endemic species. There are pine trees scattered among what seems to be the surface of the moon. The mammillarias grow in rocky shale with shallow soils mostly devoid of organic matter. Most plants grow on the tops or slopes of the barren hills.
 
Facing few threats in situ due to poaching, the flat geophytic habit of the plant may actually hide further distribution ranges. The area in which this species is recorded has been reduced to a mere 10 square kilometers. M. bertholdii may have a chance to avoid future human threat, just because the plants managed to evade over 300 years of detection! The Mexican government does not even know the species' location.
 
To give some clarity, M. bertholdii has been classified as part of the Saboae Group, which has beauties such as M. theresae and many subspecies of M. saboae. These species are generally found in the volcanic belt in the Sonoran/Chihuahuan Desert regions of Mexico, while M. bertholdii is found further south in a diverse region in Oaxaca.
 
This is seen as unusual, in that there are no known transitional species for the group between those regions. In other words, there may still be undiscovered species within the group -- or taxonomists have incorrectly placed M. bertholdii in the Saboae Group! An author has proposed that the plant may actually belong to an ancestral clade.
 
If you are lucky enough to have obtained this elusive species in the hobby, the plants' care is fairly easy. Since M. bertholdii is almost always offered as a grafted plant, we will focus on this cultivation method.
 
As a grafted plant, M. bertholdii is quick to grow and divide. The plants are quite indestructible, it seems, as our grafted plant was knocked back to a couple of sad tubercles due to spider mites and came back to a full, large plant in a matter of months.
 
M. bertholdii grows in full sun, and is not shy to take on gratuitous amounts. Avoid full sun and extreme heat, but the pectinate eyelashlike spines do help shade the body of the plant. Remember, you are watering the bottom rootstock to sustain the top scion cactus. Identify and understand your rootstock cactus, and ensure the scion gets enough light to avoid etiolation.
 
Watch out for several major pests: spider mites and mealy bugs. They can quickly ravage the plant, as tubercles seem to abort to help save the plant. Quick treatment will keep the plant alive and let you come to the calm realization that the plant will continue to grow. In time, mature growth with part of the rootstock intact could be grown on its own roots. Simply place in a well-drained substrate and do not water until roots appear.

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If your grafted plant is not very tough, chances are its vigor is diminished due to overpropagation. Experienced in the cacti hobby and with other plant families with rarer species in high demand, the issue is that vigor is reduced when some plants have been divided, grafted, divided and grafted, again and again. If they were instead micropropagated, vigor could be maintained or even increased. Don't feel bad if you are doing everything right, and your plant dies, because the cause may not be you!
 
M. bertholdii is very infrequently offered on its own roots. Plants on their own roots without definite greenhouse provenance are typically illegally pillaged plants. At all costs, do not buy these plants. Responsible seed collection by authorized personnel is the only acceptable way for these plants to enter the hobby.
 
In the event you had a spare $150 to buy a plant grown from seed on its own roots, your purchase should be hardy. However, M. bertholdii are seldom offered as seed-grown plants, since they are cryptocarpic -- fruit and seeds are produced and retained within the plant body. The seeds have inhibitors to prevent immediate germination. The plants are reportedly sensitive to overwatering. In winter, they retract in size, so avoid watering.
 
Since this species is so new and its location kept secretly protected, there is little more to learn about M. bertholdii at this time. The future may hold some interspecific crosses between the Saboae Complex that verify its place in the genus. We can hope to learn of how unique regions influence endemic species, and possibly apply this assessment to predicting where other undiscovered diminutive species may lie waiting.
 
Sources:
Llifle Encyclopedia of Cacti -- http://www.llifle.com/Encyclopedia/CACTI/Family/Cactaceae/3 2468/Mammillaria_bertholdii
Xerophilia, March 2017 -- Mammillaria bertholdii Linzen, Three Years After Its Description --
http://xerophilia.ro/wp-content/uploads/2017/03/xerophilia-2017.03-20.pdf
 

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February 2019 -- Aptenia

By Bob Williams
 
When planning our rock gardens, we carefully choose plants that we hope can survive our St. Louis winters. For the start of 2019, it seems that wet and cloudy is the norm, with a blast of extreme cold. Cheer up, it could be worse. As some of you may know, I have a cabin just north of Bemidji, Minnesota. As I wrote this article, the forecast for Jan. 29 there was for a high of minus 23 degrees F with wind chills in the minus 50s.
 
We all know that rock gardens are not maintenance free. Besides replacing the few plants that throw in the towel every year, you can add succulent ground covers for a splash of color and that "new growth" green that accents the cacti and larger succulents in our gardens. Apentia is one genus of accent plants that one should consider planting in the spring.
 
Apentia is a member of the Aizoaceae family. It is a small genus with only four species. In 2007, the genus was transferred into Mesembryanthemum. Two years later, other authors proposed that the move be reversed. So back it went.
 
Apentias are native to South Africa, mainly the Eastern Cape region. They are found mainly along the coastal areas. The genus name is from the Greek "a" (not) and "ptenos" (winged), and refers to the wingless seeds.
 
All four species remain low to the ground, growing no more than 4 to 5 inches tall. The low stems root rather easily when touching the ground. The plants can take full sun but grow well under trees and shrubs where they get bright light. The leaves are thick and fleshy with a waxy look. Apentias like well-draining soil, but can take heavy rains.
 
Once they get established in the spring, they can spread quickly, forming a thick mat. In our area, they can grow to about 2 feet in diameter. Keeping the plants in check is fairly easy; you can snip the stems, which break off easily.
 
Apentias provide ground cover that is hardy to 20 degrees F. Where they can survive year round, they are used as a ground cover in traffic islands. If you wanted to overwinter in this area, a good cover mulch may keep the root crowns from dying. In the spring, new growth will emerge. Placing a hot box over a small section could also work.
 
Taking a few cuttings, putting them in a pot and overwintering indoors is most likely the best way of having plants for the next year. It is probably a good thing that they are an annual in our area, as they are considered an invasive species in California and said to outgrow vinca.
 
As noted above, there are four species in the genus. A. cordifolia is the most common species. The plant has solitary, daisylike pink or purple flowers. In African lore, this species is used medicinally as an anti-inflammatory, a dressing and a deodorant. It is also used as a love and good luck charm. Zulu medicinal uses include a mild enema for babies. The black powder is used for vaccination and against witchcraft. Burnt stems and leaves are applied to aching joints.
 
A. geniculiflorais has white to pale yellow flowers. A. haeckeliana has flowers that are pale yellow. A. lancifolia has magenta flowers with narrow or lance-shaped leaves. As you can see, you can have a wide variety of color from these four species. Some variegated hybrids are also available. These plants flower all summer.
 
From what I can tell, apentias are widely available in the spring. They go by various names, including baby sun rose, noon flower, heart-leaf iceplant, dew plant, red apple and rock rose.
 
It is not too early to start thinking about ground covers for our rock gardens. For a hardy plant that can provide a range of color and that "succulent" look we want, apentias are an excellent choice.
 
Sources:
Llifle Encyclopedia of Cacti -- http:// www.llifle.com/Encyclopedia/SUCCULENT S/Family/Aizoaceae/28876/Aptenia_cordifolia
PlantZAfrica.com -- http://pza.sanbi.org/aptenia-cordifolia
The Plant List -- http://www.theplantlist.org/tpl1.1/search?q=apte nia
 

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