Enviro Monday: SA’s 10 worst invasive alien plants

There are approximately 27 000 indigenous species in South Africa and 9 000 foreign plant species that have been introduced over the past few centuries. Of these 9 000 exotic or alien introductions, 348 have been identified as ‘bad’, ecologically damaging, invader plants.

A total of 198 of the worst invasive alien plant species have been declared illegal weeds.

As most ecologically aware gardeners already know, getting rid of invasive alien plants (IAPs) is not so easy. Their roots are invasive and their seedlings pop up all over the garden. A number of physical and chemical techniques have proven highly effective. The key to success is to persevere in your programme of eradicating IAPs. Keep removing seedlings and remember to repeat spraying with herbicides at the intervals recommended.

Categories of invasive alien plants (IAPs)

The 198 problem plants have been divided into three categories.

Category 1

These IAPs may no longer be grown anywhere in South Africa. If they are in your garden, they should be removed and destroyed immediately. Trade in these plants is prohibited.

Cat's claw

Cat’s claw



Pampas Grass

Pampas grass

Water lettuce

Water lettuce



Indian shot (Canna lily)

Indian shot (Canna)

Ginger Lily

Ginger lily

Fountain grass

Fountain grass

Spanish broom

Spanish broom

Category 2

Primarily plants of commercial value to forestry and agriculture, these IAPs must be removed from suburban gardens and can only be grown with a permit in public spaces such as parks, schools and hospitals.

Category 3

These IAPs are permitted to grow where they already exist. However, no propagating, new planting or trade is permitted.

Why are IAPs a problem?

Invasive alien plants are highly adaptable, vigorous growers that easily invade a wide range of ecological niches.

  • They have invaded and taken over 10% of the country. This is well over 10 million hectares of land (or an area the size of KwaZulu-Natal).
  • They use 7% of the water resources in South Africa. This is roughly the same amount of water needed by humans to survive in this country.
  • They threaten our rich biodiversity by replacing indigenous and endemic vegetation. This will result in a loss of insect species that are dependent on these plants and the ripple-effect loss of the birds, reptiles and mammals that feed on those insects.
  • They invade land better used for crops and livestock grazing.
  • They are often toxic to man or animals.

Source: Life is a garden


Caxton Central

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