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Weedbuster Week (October 13-19, 2008) is a national campaign driven by the Department of Water Affairs and Forestry. The aim is to raise awareness about invasive alien plants and the problems that they cause, when they take over large tracts of land.
There are 27 000 plant species that are indigenous to South Africa and over 9 000 exotic or foreign plants in the country. Only 300 of these are regarded as a problem.
Why are the 300 invasive alien plants such a problem? Primarily because they can flourish without natural enemies, use large amounts of our scarce water and edge out or dominate ecosystems previously rich in a biodiversity of indigenous flora and fauna.
Among the worst invaders in the Western Cape were brought in by the forestry industry more than a century ago. They include natives of Australia such as the Port Jackson willow (Acacia saligna), black wattle (Acacia mearnsii), longleaf wattle (Acacia longifolia), spider gum (Eucalyptus lehmannii), sweet hakea (Hakea drupacea) and rooi-krans (Acacia cyclops).
Other invasive aliens were brought into the country as garden ornamentals that have since escaped into the veld and are causing havoc in many ecosystems. These include the lantana (Lantana camara), single pink oleander (Nerium oleander) and Spanish broom (Spartium junceum). The bugweed (Solanum mauritianum) came in with cattle feed and is now a huge problem in the Cedarburg and Outeniqua mountains.
Among the worst aquatic invaders are the parrot's feather and water hyacinth, both of which cover dams in foliage, disrupting water sports and preventing sunlight from penetrating the water.
There are a host of water wise exotics and indigenous plants that flourish in local gardens and do not cause environmental problems. The "Plant Me Instead" campaign being run by the Working for Water Nurseries Partnership Programme is a joint venture between government and the gardening industry.
It aims to protect our natural resources by promoting the removal of listed invader aliens and replacement of these problem plants with a wide variety of water wise non-invasive alien (otherwise referred to as exotic) flora and indigenous water-smart plants.
In place of the lantana, for example, plant the glorious blue plumbago, a sprawling shrub that flowers all summer. In place of the silver-leafed bitter apple, a poisonous member of the Solanum family, choose to plant agapanthus.
While the frilly double-flowered variety of oleander is sterile and therefore not a problem, the single flowered oleander (Nerium oleander) is a problem invader, particularly in the river valleys of the Cape. The plant has to be removed by law and is best replaced with an indigenous water wise shrub such as the Pride of De-Kaap, a sprawling shrub that is a native of the Kaapmuiden and Barberton areas of Mpumalanga.
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