Adeniums

Ornamental Adenium Tree

The Adenium genus is made up of tiny evergreen tree from the dogbane family.  The succulent trees come from Africa where they can be found in the Sahel (the semi-arid strip running along the south of the Sahara) and similar dry scrublands down the continent to South Africa.  The most famous species is Adenium obesum, a little shrub which grows from 1 to 3 meters (3 to 9 feet) in height and bears dazzling five petaled flowers that look like glowing stars of pink, red, and white. The flowers are widely cultivated as houseplants known as the desert rose (although they are in no way closely related to true roses).  A whole group of enthusiasts hold contests to determine who can hybridize the prettiest flower or cultivate the most striking ornamental bonsai trees.

In addition to their dazzling flowers, Adenium plants are known for having bulbous interestingly-shaped caudexes.  A caudex is the woody barrel-like stem/trunk in which certain desert trees and shrubs store precious liquids. Adeniums are very lovely but their loveliness should not obscure the fact that the wild specimens survive in one of the more punishingly competitive ecosystems on Earth–where all sorts of hungry grazers are desperately looking for meals.  To survive in Africa’s scrublands, Adeniums are not only hardy plants which can live almost anywhere on very little water, they are also poisonous.  Adeniums produce a cocktail of cardiac glycosides-compounds which affect the electrophysiology of the heart. Although these molecules (and other related cardiac glycosides such as those found in the foxglove) can be therapeutic in very tiny doses for certain heart conditions, in larger doses they are poisonous and cause the heart’s rhythm to fail altogether.  Thus, a plant known to American housewives as an frou-frou ornamental houseplant is known as the source of horrifying arrow poison to many of Africa’s toughest native hunters, who use the compound to kill big game.

San hunters of the Kalahari