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Adenium, different roses from the desert
Andrew Troubatchov
Yellow Green Exotic Garden
[email protected]
February 8, 2016
Adenium is a member of Apocynaceae family close related to oleander, allamanda, plumeria and periwinkle. Adenium native to deserts of east and south Africa and Arabian Peninsula that includes Oman, Saudi Arabia and Yemen. They are pachycaul, monoecious and briefly deciduous succulent shrubs or trees with a distinct swollen base, much of which is underground in natural setting. Above the ground a short, thick and fleshy stem can be almost globose to conical. It varies from species to species dramatically, narrowing before dividing in to numerous irregularly spaced branches. Branches are smooth, green to grayish-green with rather small, terminal, glossy or pubescent leaves.
​The name Adenium is derived from the arabic name for this plant, which means Aden, the old name of Yemen. In their native environment the plants are very variable in appearance and slow growing, but long lived, surviving for a hundred or more years. Most variety of Adenium produce varying quantity of milky sap, that can cause skin irritation because of some toxic properties and if consumed will cause more serious internal poisoning.
The leaves of most varieties are crowded together at the end of the branches, they are fleshy, shiny or have different shades of green. Some have a bit of their underside with visible veins through the surface of the leaf. Leaf type is simple, up to 4-5 inch long and 1/4 - 3 inch wide. Shape can be from spathulate to obovate, oblong or obovate, a lot depends on the variety or mix. The apex is rounded in most cases and the base tap ers into petiole.
 In the winter months Adenium usually looses all of their leaves and will go in to dormancy if temps will go down to upper 30sF in night and below 60sF at the day time. In conditions of SFL, Adenium is capable of keeping all or almost all of their foliage through the winter if temperature is sufficiently warm and may even keep blooming (mature plants). 
Just like all other members of Apocynaceae, flowers of Adenium are salver-form, tub-like at the base, with flared lips and range in color from pure white, through different shades of red, to lavender, purple and even yellow with hybrids that comes in unlimited variation of color blends and can be up to 4 inch in diameter. Some have been reported to have an attractive fragrance. 
Usually clusters of flowers are produced during the year, with more intensive production in the spring and fall months, with a little break in  mid summer, of course that is varied dramatically from species to species. 
​In SFL the most flowering occurs in the early spring months in (february_may) and drier months in the fall( november_december). Some varieties in their peak spring flowering times can be, at times, almost totally covered in blooms.
Most plants that are available today have been selected for their superior flower pattern, size or color. Some of selected clones can flower almost all year round, with lowest flower production in mid summer here in conditions of SFL. In the wild flowers are moth pollinated by a specific moth, in  a captive environment these plants are hand pollinated for breeding purposes. I personally have  great success using a simple tool_the tip of a plastic label that normally use to identify the plants. With a little practice and understanding of the mechanics of cross pollination, anyone can achieve good results with it. The fruits are usually born in pairs resembling horns at the beginning stage. They are slender follicles, each up to 3-7 inch long and 1/2 - 3/4 inch wide. 
I want to point out a couple of different types of ingredients responsible for and important to properties in a potting mix. A coarse grade and inorganic materials such as coarse sand, gravel, pumice, perlite and river rock that will provide strength, support and good drainage with aeration. Then there are organic components such as peat moss, top soil, bark (composted and fresh), coir or coconut husk fiber, humus and fine clay. The ratio of organic and non-organic components should be 1:1 if one wants to grow Adenium plants outside in conditions of SFL, with complete exposure to summer rain.  
The most important aspect in building a good mix for Adenium is to have a good, balanced structure with water coming and going without hesitation because these plants are equipped with heavy top roots that enable them to resist drought to a remarkable degree, and their leaves may have a bit of a waxy coating to adapt them to dry conditions. These are truly tough plants that can rarely be affected by anything other then overwatering.
Most growers of Adenium plants are highly appreciate impressive blooming every spring, but, depending on variety, fat caudex is often the main attraction for the rest of the year. Plants propagated from seeds, not from cuttings have known to develop above ground caudex, the feature that becomes recognizable after 2-3 years of steady growth. Root-bound contained plants is generally recommended. 
When they mature they split along one side, usually on the top, to release the seeds. The seeds are different shades of brown, sometimes darker or lighter with long silky hairy tuffs at both ends of the seed. 
​In SFL Adenium is generally cultivated in containers, but they will successfully grow in the ground in free drained mix. Unglazed, ceramic containers are ideal, but also can be grown in pretty much any type that will permit good drainage. Potting soil for Adenium plants should provide support, retain H2O and nutrients and most important has a coarse structure that provides good drainage, meaning that water applied on the surface of the pot must go through and disappear in a few seconds. The ingredients of that mix should be accessible, readily available and not expensive. 
With regularly watering and fertilize it will attain the desired size. If repotted frequently(every 2-3 years) and raising the plant at each repotting will help to develop impressive caudex. On the other hand, keeping Adenium plants root bound without repotting is one of the way to cultivate “bonsai” style. 
The most reliable propagation is by seeds achieved by hand pollination, because fresh, viable seeds, when planted properly, will have a high rate of germination and on top will adopt to unique conditions of the grower from very the beginning of their life. When germinating seeds, attention must be paid to a cleanliness of containers, soil, and the rest of the materials that are involved in the process. For example, when I germinate my seeds I use only brand new containers and labels, never reused ones, plus my germinating mix is coir from sterilized bag and coarse perlite, 1:1.
I use small square or round plastic pots for my germination, I fill my pots up to 3/4 with my germination mix (coir/perlite) and place them in the water trays overnight, make sure the substrate is constantly wet. 
When I place my seeds on the surface i apply simple water mist on top of it to moisten them evenly and then i put my pots in ziplock bag, close close bag tight and leave them for a few days or more on the bright lighted place, but without direct sun, before they will start to germinate. The major advantage of growing Adenium from seeds is that the genetic of each seed is different and growing plants will be similar in some ways, but also slightly different. Some of a new seedlings may inherit characteristics of one  parent and others the other parent and some will have characteristics of both parents or something new with mix characteristics of both parents.
In complex cross breading a very small percentage of offsprings will inherit the best traits of both parent. i find it extremely interesting and rewarding to grow from seeds and it will be significantly less expensive to compare if one was to purchase an already established specimen or even a young (2-3 years) plant. 
The success for growing Adenium is in the SFL climate (wet/dry pattern) to their advantage and adapting to some disadvantage of the rainy season. One of the important aspects of an environment is a dry and sunny season very much favorable to Adenium growing. Watering in the right time and with the right amount, allowing plants to properly dry before the next watering is the key to that success. Growers with experience will never judge by the way the surface appears in the growing media of the pot but will probe for the weight of the pot for small containers (when pot is dry it weighs less then when its wet) or a simple, but very good tool, like a pencil to probe a couple of inches deep in the pot. If it comes back as dry, the answer is this plant need a good drink. Watering  Adenium plants properly is as important as much as allowing it to dry out and this process must be done in the proper way as well. For that purpose a correct watering device at the end of the water hose is very important. Usually it looks like a shower head with numerous little holes that will break the water flow into numerous streams and allows more contact between the water and the plant roots, media and the pots. The proper way to water Adenium will be to water each pot until water will flow freely from the bottom of the pot. As soon as the grower sees that he should move to the next pot and repeat again and move to the next and repeat again to each and every pot. Sometimes it may take two or more tries to see that water will flow through  and out from the bottom. 
Adenium plants are heavy feeders in general terms to compare to other caudex forming succulents and they appreciate a shot of fertilizer from spring to fall on a regular basis.
There are several varieties that are known to cultivation and of course there are hundreds of hybrids of all kinds.

A. arabicum is from Arabian Peninsula, where it naturally occurs in deserts of south west of the region. It has most squad and massive caudex with numerous basal branches with usually pubescent with rounded tips leaves that somewhat large in the size. Flowers are usually around 2 inch in diameter, rounded petals, pale to bright pink, sometimes sometimes even white. Plants usually start to flower at the end of dormancy or early spring. 

A. boehmianum is naturally occurring in south west side of Africa, with limited distribution in Namibia and Angola. Growing habit is erect, branched, with poorly developed caudex. Rare in cultivation, fast grower, but has very short growing season in mid summer with large leaves and  flowers are similar in structure to flowers of A. swazicum. They are solid colored, overlaped petals are from almost white to medium pink with dark throat, around 2 inch in diameter. Plants begin to flower in mid summer and flower profusely through fall.

A. crispum distribution is limited to semidesert areas of deep red sand of Somalia. It has dwarf growing habit with napiform subterranean, partially exposed caudex and a few aboveground stems that are erect and normally only 8-10 inch long with very narrow linnear leaves that usually are prominently white veined and strongly crisped. Flowers are small, diminutive, starlike shape, usually about 1 1/4 -1 1/2 inch in diameter with margins of the petals curled downward, light pink to dark red in color. 
The nectar guides in the throat extend to the tips of the petals giving the flowers a striped appearence. Flowering season starts in mid summer and goes through late fall.{cke_protected}{C}%3C!%2D%2D%5Bif%20gte%20vml%201%5D%3E%3Cv%3Ashapetype%0A%20id%3D%22_x0000_t75%22%20coordsize%3D%2221600%2C21600%22%20o%3Aspt%3D%2275%22%20o%3Apreferrelative%3D%22t%22%0A%20path%3D%22m%404%405l%404%4011%409%4011%409%405xe%22%20filled%3D%22f%22%20stroked%3D%22f%22%3E%0A%20%3Cv%3Astroke%20joinstyle%3D%22miter%22%2F%3E%3Cv%3Aformulas%3E%3Cv%3Af%20eqn%3D%22if%20lineDrawn%20pixelLineWidth%200%22%2F%3E%0A%20%20%3Cv%3Af%20eqn%3D%22sum%20%400%201%200%22%2F%3E%0A%20%20%3Cv%3Af%20eqn%3D%22sum%200%200%20%401%22%2F%3E%0A%20%20%3Cv%3Af%20eqn%3D%22prod%20%402%201%202%22%2F%3E%0A%20%20%3Cv%3Af%20eqn%3D%22prod%20%403%2021600%20pixelWidth%22%2F%3E%0A%20%20%3Cv%3Af%20eqn%3D%22prod%20%403%2021600%20pixelHeight%22%2F%3E%0A%20%20%3Cv%3Af%20eqn%3D%22sum%20%400%200%201%22%2F%3E%0A%20%20%3Cv%3Af%20eqn%3D%22prod%20%406%201%202%22%2F%3E%0A%20%20%3Cv%3Af%20eqn%3D%22prod%20%407%2021600%20pixelWidth%22%2F%3E%0A%20%20%3Cv%3Af%20eqn%3D%22sum%20%408%2021600%200%22%2F%3E%0A%20%20%3Cv%3Af%20eqn%3D%22prod%20%407%2021600%20pixelHeight%22%2F%3E%0A%20%20%3Cv%3Af%20eqn%3D%22sum%20%4010%2021600%200%22%2F%3E%3C%2Fv%3Aformulas%3E%3Cv%3Apath%20o%3Aextrusionok%3D%22f%22%20gradientshapeok%3D%22t%22%20o%3Aconnecttype%3D%22rect%22%2F%3E%0A%20%3Co%3Alock%20v%3Aext%3D%22edit%22%20aspectratio%3D%22t%22%2F%3E%3C%2Fv%3Ashapetype%3E%3Cv%3Ashape%20id%3D%22officeArt_x0020_object%22%20o%3Aspid%3D%22_x0000_s1027%22%0A%20type%3D%22%23_x0000_t75%22%20style%3D'position%3Aabsolute%3Bmargin-left%3A-11.05pt%3Bmargin-top%3A246.6pt%3B%0A%20width%3A244.3pt%3Bheight%3A244.3pt%3Bz-index%3A251678720%3Bvisibility%3Avisible%3B%0A%20mso-wrap-style%3Asquare%3Bmso-wrap-distance-left%3A12pt%3Bmso-wrap-distance-top%3A12pt%3B%0A%20mso-wrap-distance-right%3A12pt%3Bmso-wrap-distance-bottom%3A12pt%3B%0A%20mso-position-horizontal%3Aabsolute%3Bmso-position-horizontal-relative%3Amargin%3B%0A%20mso-position-vertical%3Aabsolute%3Bmso-position-vertical-relative%3Aline'%0A%20wrapcoords%3D%220%20-4%2021596%20-4%2021596%2021591%200%2021591%200%20-4%22%20strokeweight%3D%221pt%22%3E%0A%20%3Cv%3Astroke%20miterlimit%3D%224%22%2F%3E%0A%20%3Cv%3Aimagedata%20src%3D%22file%3A%2F%2F%2FC%3A%5CUsers%5CAlexy%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_image001.jpg%22%0A%20%20o%3Atitle%3D%22%22%2F%3E%0A%20%3Cw%3Awrap%20type%3D%22through%22%20anchorx%3D%22margin%22%20anchory%3D%22line%22%2F%3E%3C%2Fv%3Ashape%3E%3C!%5Bendif%5D%2D%2D%3E{cke_protected}{C}%3C!%2D%2D%5Bif%20!vml%5D%2D%2D%3E {cke_protected}{C}%3C!%2D%2D%5Bendif%5D%2D%2D%3E{cke_protected}{C}%3C!%2D%2D%5Bif%20gte%20vml%201%5D%3E%3Cv%3Ashape%0A%20id%3D%22_x0000_s1026%22%20type%3D%22%23_x0000_t75%22%20style%3D'position%3Aabsolute%3Bmargin-left%3A244.35pt%3B%0A%20margin-top%3A267.7pt%3Bwidth%3A223.15pt%3Bheight%3A223.15pt%3Bz-index%3A251679744%3B%0A%20visibility%3Avisible%3Bmso-wrap-style%3Asquare%3Bmso-wrap-distance-left%3A12pt%3B%0A%20mso-wrap-distance-top%3A12pt%3Bmso-wrap-distance-right%3A12pt%3B%0A%20mso-wrap-distance-bottom%3A12pt%3Bmso-position-horizontal%3Aabsolute%3B%0A%20mso-position-horizontal-relative%3Amargin%3Bmso-position-vertical%3Aabsolute%3B%0A%20mso-position-vertical-relative%3Aline'%20wrapcoords%3D%22-5%200%2021595%200%2021595%2021600%20-5%2021600%20-5%200%22%0A%20strokeweight%3D%221pt%22%3E%0A%20%3Cv%3Astroke%20miterlimit%3D%224%22%2F%3E%0A%20%3Cv%3Aimagedata%20src%3D%22file%3A%2F%2F%2FC%3A%5CUsers%5CAlexy%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_image003.jpg%22%0A%20%20o%3Atitle%3D%22%22%2F%3E%0A%20%3Cw%3Awrap%20type%3D%22through%22%20anchorx%3D%22margin%22%20anchory%3D%22line%22%2F%3E%3C%2Fv%3Ashape%3E%3C!%5Bendif%5D%2D%2D%3E{cke_protected}{C}%3C!%2D%2D%5Bif%20!vml%5D%2D%2D%3E {cke_protected}{C}%3C!%2D%2D%5Bendif%5D%2D%2D%3E
A. obesum is the most popular, but also the most variable of all Adenium by growing habit and colors of flowers. It normally produces very nice caudex and profuse basal branching with leaves that range from narrow to broadly obovate that is a deep shiny, leathery green. Flowers are vary from pure white to pink and from intense pink to deep red with all types of possible shades and tones with size around 2 1/2 - 3 1/2 inch in diameter. The typical flowering pattern for A. obesum is high peak in spring, slows down in the mid summer and second spell in fall.
A. socotranum is endemic to the island of Socotra that is in the Indian Ocean, near the south coast of Arabian peninsula. This variety is the largest of them all, resembling small baobab tree with conical trunk several yards tall. It is rare and new to cultivation with a slow growing rate with strongly vertical habit of growth. Leaves are dark green and has whitish mid rib and major veins. Flowers are around 3 inches in diameter and varies from pale to medium pink with darker throats and prominent nectar guides. Spring is the flowering season for this species.

A. somalense is distributed around the east side of central Africa, through Kenia, Tanzania and Somali and parts of Ethiopia. It has upright growing habit with very wide based distinct conical caudex that thickens rather slowly. The long narrow leaves are bright green and have prominent white veins. Flowers are normally around 2 inches in diameter with narrow, pointed petals and prominent nectar guides, with color varies from light pink to deep red. flowering season is in summer months, when peak will be in June-July and some more in the fall.

A. swazicum is native to the east coast of southern Africa, Swaziland and some parts of Mozambique. This is a short stemmed variety with subterranean caudex that can be massive with age.
The long and narrow leaves are light green, fuzzy underside and tend to be slightly folded upward along the midrib when exposed to a strong afternoon sun. Flowers are usually round with uniform color from petal margin to the edge, around 3 inches in diameter, usually lavender-pink to deeper pink, some are almost purple or crimson. Flowering season start at the end of the summer and intensifies in the early fall.