Municipal Plant of the Month – Oleander: Nerium oleander. This plant threatens the ecology of river valleys which is of particular concern in our dry country. Its robustness, resistance to disease, and tolerance to adverse soil and climatic conditions make it difficult to control. It is listed as a Category 1b invader and habitat transformer and must be removed and destroyed. Any form of trade or planting is strictly prohibited. Oleander is one of the most poisonous of commonly grown garden plants. All parts of the plant are extremely toxic and lethal, and the sap is a skin irritant.
Impact: Invades watercourses in the semi-arid areas of the Little Karoo and in Gauteng. The primary invader is the pink flowered variety – clearly evident along the Nels River outside Calitzdorp and the river valleys of the Kamanassie region.
Identification: The foliage is slender, leathery dark green leaves. Overall appearance is that of a large robust shrub (up to 6 m tall) with an abundance of pink, red or white flowers. The fruits are red-brown in colour, split length-wise when ripe exposing the seeds that have tufts of hair.
Control: The plant coppices when cut back, complicating control. No specific herbicide is registered for the control of this invader weed although there are herbicides that are registered for total weed control which could be used. However, great care needs to be taken with their use to avoid damage to other species. The tufted seeds are wind and water-dispersed, therefore recognising and weeding seedlings before they become too large is the best approach. Large plants need to be removed entirely.
References: www.invasives.org.za : www.sanbi.org