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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 2018 -- Cleistocactus

By Rey Gonzalez
 
Cleistocactus is a columnar member of the Cactaceae family described by Curt Backeberg in 1913. It is native to the mountainous areas of Peru, Uruguay, Bolivia and Argentina, and can be found growing in large, shrubby clumps mixed in with other vegetation or clambering over boulders. The name Cleistocactus comes from the Greek "kleistos," meaning "closed cactus," a reference to the appearance of the flowers.
 
Some might say that Cleistocactus is a genus of quantity over quality, because many of the features of this genus are small, but profuse. The stems are typically from 1 to 2.5 inches or so in diameter, but branch readily at the base to form noticeable clumps. In general, the spines are likewise small and flexible, but in most cases, are very numerous -- even to the point of obscuring the stems.
 
Many species have flowers that resemble little tubes of lipstick or firecrackers. The tubular, rose-red flowers are about 3.2 inches long and are scattered along the stems.
 
Several species are extremely popular in cultivation and are among the most common cacti in nurseries worldwide. The two most popular of all are Cleistocactus strausii and C. winteri. Species like C. strausii can reach a height of over 10 feet, while C. winteri and others are branching cacti with spreading, arching, pendant or trailing stems that grow up to 40 inches long and 1 inch wide.

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To grow Cleistocactus plants, choose a location that gets full sun and has well-draining soil. Water them during spring and summer, when the top inch of soil dries out. During the fall, reduce watering to every four to five weeks if the ground dries out.
 
In winter, keep the soil dry to prevent root rot. Cool temperatures combined with moist soil and dormancy can cause the roots to rot. A slow-release fertilizer applied in the spring will be sufficient for the whole year.
 
It is possible to propagate by cutting a small branch from a cleistocactus and rooting it, but this inevitably leaves a disfiguring scar near the base of the main stem. If an offset is removed to be used in propagation, remember to dry it for a week or so, letting the wound heal. Rooting usually occurs within three to eight weeks. All Cleistocactus species can be susceptible to mealy bugs and spider mites.
 
Sources:
Rikke's Plants: Cleistocactus strausii -- http://www.bihrmann.com/rikke/subs/cle-str-sub.asp
Ecology & Evolutionary Biology Conservatory -- https://web.archive.org/web/20051101024213/http:/floraw ww.eeb.uconn.edu/acc_num/198502128.html
World of Succulents: Cleistocactus winteri -- Golden Rat Tail -- https://worldofsucculents.com/cleistocactuswinteri-golden-rat-tail/
 

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February 2018 -- Adenia

By Bob Williams
 
Sometimes botanists like to play cruel jokes on people. Mention the genus Adenia to most people, and more often than not, you will be corrected that the name is Adenium.
 
Both genera can grow impressive caudices. They lose their leaves in the winter. They can grow fast. That is where the similarities end.
 
Adeniums are known for their flowers. The flowers of Adenia are small and non-descript, but plants in the genus have things going for them that make them attractive to the caudex-loving individuals among us. They seem to be hardy. They grow fast. They can form a large caudex.
 
Adenia is a genus of flowering plants in the passion flower family, Passifloraceae. The genus name Adenia comes from "aden," described as the Arabic name for the plant by Peter Forsskål, the author of the genus.
 
All adenias are perennial plants, but there are many different forms, including herbs, vines, shrubs and trees. Many are succulents, and some are pachycauls with thick stems and few or no branches. Some have fibrous root systems, and some have tubers.
 
Adenia plants can be found in a wide variety of habitats, from the dry African deserts to wet Southeast Asian rainforests. There are some 100 species in the genus.
 
Adenias are strange plants. They have medicinal uses, yet many species are toxic. Several species are used in traditional African medicine. Various parts of A. cissampeloides are used to treat conditions that include gastrointestinal problems, inflammation, pain, fever, malaria, leprosy, cholera, anemia, bronchitis, sexually transmitted diseases, and mental illness.
 
A. dinklagei leaves are ingested to treat palpitations. The leaves of A. tricostata are used to treat fever. The leaves or leaf sap of A. bequaertii are taken to treat headache and mental illness. A. lobata stems are applied to sites of Guinea worm infection and are used as an enema and an aphrodisiac. A. cissampeloides is used as a fish poison and arrow poison. The fruit of A. digitata has been used in Africa to commit homicide and suicide.
 
The toxicity can come from sap like a euphorbia or from ingesting leaves or fruits. Handle this plant group with care.
 
The Adenia plants that those in the hobby covet mainly grow in southern Africa and Madagascar. In habitat, they are often found in brush, with the branches scrambling up through the bushes. When growing in open areas, the plants form their own "bush," with new growth from the base coming through mostly dead stems.
 
This creates something of a dilemma for growing these plants. They are shrubs or small trees that grow in a hot, full-sun environment, yet their caudices are almost entirely shaded. Full sun will "sunburn" the base.
 
Adenia plants should be grown in bright, indirect light or under shade cloth. Like most succulents, they like fast-draining soil and frequent watering during the summer. I read that they can take watering every four to five days. Only water when the soil has dried, though. Do not keep the soil constantly moist.
 
When the weather turns cool, these plants lose their leaves. Quit watering. They can get by in the winter with no water. Cold, soggy soil is a death sentence for these plants. They are not cold-hardy for this area and should be sheltered or brought in before temperatures drop to 45 degrees F or below.
 
Once the leaves fall, you can prune the vines back from 6 to 12 inches. Adenias flower in the spring, but apparently the flowers are nothing to write home about.
 
Propagation can be by either stem cuttings or seed. When doing stem cuttings, the odds of a caudex forming are low. If trying to propagate by seed and you want to do your own pollination, adenias have male and female plants, so you need one of each. In reading about care for this plant, I found they like a soil ph between 6.1 and 6.5.
 
As I said, these plants can grow fast. Most can form a caudex 6 feet in diameter and up to 2 feet tall. Some information suggests that repotting every two or three years may be required because of this rapid growth.
 
Some of the more commonly grown Adenia species are A. glauca, A. aculeate, A. globose, A. digitata, A. pechuelii and A. spinosa. They can be found fairly easily for sale.
 
Overall, there is not a large amount of information available on these plants. I am not sure why. Maybe it got posted under Adenium.
 

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February 2018 -- Euphorbia coerulescens

By Joe Merkelbach
 
The name for Euphorbia coerulescens in Afrikaans, the European-created language of southern Africa, is Sweet Noor or Noorsduring. It is such a common species in the ravines and on the hilltops of the East Cape Province that the area is called the Noorsveld. The plants are more prominent on the north-facing slopes -- the sunny side in the Southern Hemisphere.
 
The "sweet" appellation perhaps has reference to the rather benign latex of the plant. The tops can be cut off the plants and allowed to wilt for a few days before being used for livestock fodder. The common name for E. coerulescens, blue euphorbia, refers to its light blue-green color.
 
In habitat, the stems grow upwards from underground rhizomes. Mature plants have a tight grouping of stems up to 20 in number and reaching 1.5 meters in height. The stems, which average 5 centimeters in diameter, can have between four and six faces with rows of paired double thorns arranged vertically in felted-looking strips.
 
The stems grow in expanded and restricted segments, looking something like etiolation due to variations in growing conditions. Specimen plants seem to be more prone to branching than naturally occurring plants.
 
The small, yellow female and brown male flowers occur in strips toward the tops of the stems. Small ephemeral leaves, only about two millimeters in length, occur on new-growth stem tips in the same locations as the flowers.
 
Euphorbia coerulescens can handle light frosts, but would not survive outside planting during our St. Louis winters. It requires good drainage, with plenty of pumice or pea-sized gravel in the potting mix.
 
Its reputation is as a relatively fast grower that requires a bit of shade when first moved outside in the spring to protect against sunburn.
 
Sources:
Cactus Art -- Euphorbia_coerulescens/Euphorbia_coerulescens/Euphorbia_coerulescens.htm
Operation Wildflower -- http://operationwildflower.org.za/index.php/albums/euphorbias/euphorbia-coerulescens-judd-8-4196#joomimg
http://operationwildflower.org.za/index.php/albums/euphorbias/euphorbia-coerulescens-e-cape-stock-fodder-poortasting-honey-il-2-3101#joomimg
http://operationwildflower.org.za/index.php/albums/euphorbias/euphorbia-coerulescens-judd-2-4194#joomimg
http://operationwildflower.org.za/index.php/albums/euphorbias/euphorbia-coerulescens-judd-7-4195#joomimg
 

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