Strophanthus kombe or Arrow Poison Tree grows in the hot lowlands of Zimbabwe with high humidity during the summer months. It is part of the genus Strophanthus which contains approximately 38 species. Strophanthus kombe is found in thicket-like forests of low height, where Acacia, Baobab and Monkey Orange trees commonly occur, or in dense under-storey. Strophanthus kombe climbs up the highest trees and hangs from one tree to another like a bush-vine. Most recognizable are its yellow-orange flowers, which have characteristic “petal tails” up to 17 cm long, from which it derives its name – strophos anthos – “twisted cord flower”.
Strophanthus kombe flowers before the rainy season prior and during leaf development. In forests, you often find two or more (up to nine) stems growing from the rootstock. The stem, twigs and pods have characteristic lenticels. Buds sit cross-opposite on branches and twigs. The bark of the young shoot is first green, later reddish-brown with velvety hair; in the second year the bark turns grey and feels corky. The leaves are large, with bristly hair on both sides and feel rough like sand paper; the dark green colour is characteristic, the bottom being brighter than the top. The fruit is elongated (about arm-length); the pods sit in pairs on a stalk, branching off the previous year’s twigs or older ones. The pods are brown when fresh and covered with almost white lenticels; the fruit have a characteristic tip, which can vary in shape and which differs from all other Strophanthus species.
What is it used for?
Both the seeds and roots of the plant have been used traditionally for thousands of years by many African peoples as the principal ingredient in arrow poison. Today, the seeds are used pharmaceutically for patients with certain heart conditions that affect blood circulation. This plant was inadvertently used as a medical experiment by Sir John Kirk, a nineteenth century plant explorer who brought back specimens of Strophanthus kombe for the Royal Botanical Gardens at Kew in London. Some of the plant’s juice accidentally landed on his toothbrush. After brushing his teeth he reported a quick drop in his heart rate. In fact, Strophantus kombe contains a cardiac glycoside which directly affects the heart. As ordinarily administered, the drug acts on the heart before influencing any other organ or tissue. Often no other action can be observed. It is used to produce the drug Ouabain which is taken as a cardiac stimulant to treat heart failure, and is similar to the drug Digoxin produced from Digitalis purpurea. Strophantus kombe has been used for two extremes: ending a life and saving a life, so proper dosage is crucial when using this plant medicinally.