Tuesday, 15 October 2019

Know your invasive species

invasive species

The invasive alien plant species covered here all reproduce and spread quickly, forming dense populations in natural habitats to replace native species and stifle their regeneration.

Category 1a and 1b invasive alien plant species (IAPs) must be removed and destroyed immediately.

Category 2 IAPs may be grown under the cover of a permit. However, the landowner must ensure that the species does not spread beyond his/her property.

Category 3 IAPs may not be planted. Some invasive plants are, however, categorized differently in different provinces.


Also known as summer lilac, Chinese sage wood (Buddleja Davidii) is a vigorous grower in well-drained soil and full sun. It can tolerate drought and grow in very challenging places, such as in cracks in the pavement and along railroads. Its leaves are dark green and shiny above, and are white and downy below, with slightly toothed margins.

The blade is lance-shaped. Its flowers are tubular, white to lilac-purple, with orange-yellow throats. They can be seen from summer to autumn. Its seed is encased in brown capsules that are 5mm to 10mm long. Each capsule contains many tiny seeds. B. David is problematic along river banks, where it forms dense thickets, crowds out native vegetation and disrupts natural ecological succession patterns. Invasive status: NEMBA Category 3; Invasive status: NEMBA Category 3; in a  problem in the problem Western Cape.



This coniferous tree (Pinus roxburghii) reaches up to 20m high or more and has a conical or oval crown. It has large, ascending branches with secondary shoots and very thick, fissured bark. Its leaves consist of light to bright-green needles that present in bundles of three and are 150mm to 300mm long. It produces light-brown cylindrical cones of 150mm to 220mm long.

The chair pine invades grasslands and is usually present on dry mountain slopes, where it competes with and replaces indigenous vegetation. Dense stands can reduce water run-off and streamflow from a mountain catchment, reducing grazing and posing a fire hazard. Invasive status: NEMBA Category 2; a problem in Gauteng.



A coniferous tree 8m to 15m high, the cluster pine (Pinus pinaster) is conical when young, becoming cylindrical with a tall, bare trunk when older. Its leaves consist of dull grey-green needles that present in bundles of two and are 80mm to 240mm long. The needles are thick and rigid. The cluster pine produces woody, purple cones that turn light brown. Dense stands can pose a fire hazard.

Invasive status: NEMBA Category 2 for plantations and wind-rows; Category 1b elsewhere. National heritage trees or national monument trees in terms of the National Heritage Resources Act (No.   25 of 1999) are excluded.

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