Invasion Biology

Saturday, July 15, 2006


We all know about Rooikrans (Acacia Cyclops) and Port Jackson (Acacia saligna) originating from Australia that have invaded many areas in the Cape Floristic Region. Many South African plants have however also become invasive in Australia. Some are even threatened species in their natural habitat in South Africa, but have become a pest in Australia. One such example is the yellow wild iris (Dietes bicolour). South African plants that have long been declared pests in Australia are for example our bitou (Chrysanthemoides monilifera) and arum lily (Zantedeschia aethiopica).

New introductions of potential weeds is however an ongoing problem. Recent South African introductions (between 1971-1995) in Australia that have already become locally naturalized are amongst others the green ixia (Ixia viridiflora), the blouooguintjie (Moraea aristata), a gladiolus from Kwazulu-Natal (Gladiolus natalensis) and a chasmanthe (Chasmanthe bicolour). Yet three of these species are red data species in South Africa! All of the above mentioned plants were introduced as ornamental garden plants but have since escaped from urban gardens and have become naturalized. (read more here)

Up until 2004 non-South African resident members of the Botanical Society of South Africa could make use of the “free seed benefit”. This meant that as members they could order a certain amount of seeds from South African indigenous plants for free on a yearly basis. This was discontinued at the end of 2004. One of the reasons was to stop the spread of potentially alien invasive weeds to other countries.

Australia now has very strict legislation to try and prevent further introductions of potentially invasive species. However, as long as there are obsessed plant collectors willing to pay, seeds and plants will find their way into other countries …

Further reading:

March 2006 issue of Veld & Flora, the Journal of the Botanical Society of South Africa.

South African Red Data List (can be downloaded at the following link: )

Karen Marais
BCB Hons NISL student
University of the Western Cape
Private Bag X17




  • I did not know that Dietes bicolour was invasive. When I was in America - I saw mostly South African plants that it made me homesick.

    By Blogger Rich Knight, at July 20, 2006 11:21 PM  

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