Greetings to all our Village plant enthusiasts. Welcome to the 4th “Plant of Interest” article for 2016!! This week we’ll be looking at a member of the Solanaceae (potato/Nightshade) family. Any plant can be of interest when it displays unique traits – always a favourite to the author, are plants that seem inconsequential at a glance, but chemically tell a whole different story – as this week’s PoI will convey.
Datura stramonium (Common Thorn Apple in English, Gewone Stinkblaar in Afrikaans and lechoe in Sesotho) is an annual weed occurring from the Western Cape through to KZN. It can be found along roadsides, old pastures and in disturbed areas at altitudes ranging from 0 – 2400 m A.S.L. It is believed to have originated in tropical areas of the U.S. but was most likely accidentally introduced to South Africa among cereal grain.
The specimen photographed here is just one of many found recently growing in the area. It is often eaten and spread by livestock, resulting in fatalities. When even a small stem is cut, it releases an acrid scent (hence the Afrikaans Stinkblaar) which permeates the air for many metres. Cutting of a large patch of the plant can result in blurred vision, proving removal challenging and is a wholly unpleasant task. From a management perspective, the plant is regarded as a weed and declared a Category 1b invasive in South Africa – the detrimental applications and implications on an economic and social scale outweigh its value greatly. It thus requires mandatory removal from all public areas and even private residences.
Many species of this family contain toxic substances such as alkaloids (see medicinal uses) many of which are intentionally and sometimes accidentally ingested. This plant is notable for its many uses in the treatment of numerous ailments as well as the psychological effects that it imbues on the user as a narcotic. As with any plant or medicine, the use of the plant is all about dosage. Even the tiniest miscalculation can be the difference between a favourable effect on the body & mind or a fatality. It is not advised to use this plant or any of its derivatives without prior professional consent.
Physiologically, the plant may obtain a height of 1.5 metres, and is much branched as a weedy shrub. It may occur in isolation but is usually observed in large scraggly patches in older stands. The ovate 4 chambered fruit (measuring approx. 50mm long by 30mm wide) are a bright green when young and covered in multiple short, nasty looking spines of around 10mm. When dry, the fruit brown and split down the centre, releasing the dark brown seed. The leaves are large – measuring in excess of 100mm by 60mm and have irregularly toothed margins. Each leave stalk holds one large purple-white tubular flower (these are closed in sunlight and open at night and in partial shade). Grows Nov – April.
Increasing number of D. stramonium in the veld is a symptom of overgrazing or degradation. This is especially of concern since the spread of this species has only been widely observed this past summer in the region, and is another indication that the cattle and goats in the reserve are indeed a factor leading to the reserves decline. Removed before a seed-bed can be accumulated, the problem can be reversed with regular follow-ups.
Dubbed “malpitte” (mad pips) in Afrikaans, the ingestion of a high dosage of this plant (as seeds) – according to one source who confessed in their youth to consuming parts of the plant – can lead to a variety of symptoms including disorientation, rage, anxiety, hallucinations, etc. At low doses extracted from the leaves it may be used as a sedative and depressant.
Traditionally, infusions have been used to relieve asthma and reduce pain. They may also be used to induce a trance for ceremonies and act as aphrodisiacs. A fresh, warmed leaf may be applied in a poultice to treat rheumatism, gout, boils, abscesses, and small wounds. The green fruit may be sucked to treat tonsillitis, sore throat and even toothache. The smoke from a dried leave is inhaled to relieve bronchitis and asthma.
At one stage extracts of the leaves were concentrated in certain cough syrups to treat respiratory difficulties; although modern cough syrups do not include the compounds from these extracts. Today, 2 compounds from D. stramonium are still commercially utilised: the alkaloids atropene, in eye-drops; and hyoscine for motion sickness. Hyoscine can also be injected in the treatment of Parkinson’s disease and painful back spasms. The pharmacological effects exerted on the human body by various parts of D. stramobium include: increased heart rate; smooth muscle relaxant, saliva, sweat and other secretant reduction, partial ocular paralyses and even glaucoma.
Not classified by SANBI, regarded as a Cat1b invasive weed according to NEMBA (10 of 2004).