Weeds in our Area (Part Ten) By Bob and Ena McIntyre – Garden Route Branch. Poisonous Plants




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Weeds in our Area (Part Ten)

By Bob and Ena McIntyre – Garden Route Branch.


Poisonous Plants
Many of our Category One Weeds (prohibited and should be removed) were introduced because they made attractive garden subjects and may not necessarily be in the top category of invaders but have other negative implications such as contaminating agricultural products, being poisonous to man and beast, causing skin and respiratory irritations, etc.
Two such weeds introduced as garden subjects are Nicotiana glauca (wild tobacco, wildetabak) and Thevetia peruviana (yellow oleander, geel oleander), both falling into the highly poisonous category. Both species are in flower during early autumn.
Nicotiana glauca is a slender evergreen shrub or small tree with blue-green leaves and yellow tubular flowers in drooping clusters. Wild tobacco can be found all over our area and has infested areas in all nine Provinces. The plant is very adaptable and can withstand arid as well as wet conditions. There have been several tragic cases of human poisoning were young plants have been mistaken for similar looking plants used as traditional cooked spinach (known as marog). One Afrikaans common name ‘volstruisgifboom’ indicates that this plant has had negative consequences for ostrich farmers in the arid regions of the Little Karoo. In Italy the plant has been used as a rat poison and dried flowers are said to be effective for killing cockroaches.
No herbicides are registered for the control of N. glauca, therefore manual weeding of young plants is recommended. Always wash hands thoroughly after handling the plants.
Thevetia peruviana is a leafy evergreen shrub or small tree characterised by its bright green leaves and beautiful yellow or orange trumpet shaped flowers with five spreading and overlapping lobes. The plant has a milky sap.
Yellow oleander is not as invasive as wild tobacco however the flowers, leaves, milky latex and particularly the seeds are extremely poisonous. It is said that four seeds could kill a child and a few leaves are sufficient to kill an infant. Ground seeds have been used as rat poison, and the seeds and leaves successfully used as a means of committing suicide. The bitter taste is a deterrent and vomiting usually prevents any serious consequences as a result of accidental intake.
The tree, although very attractive and not very invasive, has the big disadvantage of being potentially lethal to both man and beast.
Line drawings with acknowledgement to “ALIEN WEEDS AND INVASIVE PLANTS” by Lesley Henderson. Copyright © 2001 Agricultural Research Council.


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