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Top 5 Invasive Plant Species in KwaZulu Natal

In South Africa there are several Invasive Alien Plant Species (IAPS), with different IAPS being more problematic than others in each province of the country. In KwaZulu Natal there are five IAPS that are dominant across the province, inclusive of Acacia mearnsii, Chromolaena odorata, Lantana camara, Eucalyptus spp., and Solanum mauritianum (Meijninger & Jarmain, 2014).

Acacia mearnsii
Acacia mearnsii or commonly known as Black Wattle is native to Australia (Rojas-Sandoval & Pasiecznik, 2015). A. mearnsii is a perennial, woody species or shrub which is propagated through seeds (Rojas-Sandoval & Pasiecznik, 2015).
This species can be identified through its yellow globular flowers; dark brown and black seed pods (when ripe) with fine hairs; black smooth oval-like seeds; bark that is hard brownish-black in older trees and grey-brown and smooth on younger trees; and leaves that are dark green, fern-like and bipinnate (Rojas-Sandoval & Pasiecznik, 2015).
A. mearnsii is invasive in KwaZulu Natal due to its unique characteristics of long living seeds that lie dormant in the soil, and its ability to form root suckers and its ability to successfully establish in a wide range of soil conditions (Rojas-Sandoval & Pasiecznik, 2015). The seeds of the A. mearnsii are spread through various dispersal methods such as mammals, water and birds (Rojas-Sandoval & Pasiecznik, 2015)

Chromolaena odorata
Chromolaena odorata or commonly known as Jack-in-the-Bush, amongst many other common names, is native to the south-eastern portions of the United States of America, Mexico, the Caribbean and South America (BioNET-EAFRINET, 2020). C. odorata is a sprawling shrub that may form thickets and can grow 3m tall (standalone) or 20m if climbing over other vegetation and is propagated through seeds (BioNET-EAFRINET, 2020).
This plant can be identified through its small white/purple flower-heads with no petals that are usually in clusters; black or born seeds with white or brownish hairs; triangular or egg-shaped leaves that are pointed at the tip; stems that are yellowish green and may have hair in younger plants and as the plants mature the stems become woody towards the base (BioNET-EAFRINET, 2020).
C. odorata has become invasive due to its ability to form dense stands where it outcompetes and prevents the establishment of other species (BioNET-EAFRINET, 2020). The seeds of the C. odorata are spread through wind and various other mechanisms such as animals and water (BioNET-EAFRINET, 2020).

Lantana camara
Lantana camara or commonly known as Lantana is native to central and South America (Invasives, 2020). L. camara is a shrub that tends to be very untidy and spreads or scrambles (Invasives, 2020).
L. camara can be identified through its stems having recurved thorns; leaves that are dark green and hairy and tend to have a rough texture. When the leaves are crushed, they have a strong smell. The flowers are pink, red, crimson, orange, yellow or white in colour and tend to be in compact heads; and the fruits of the L. camara are glossy green and turn purple to black when ripening (Invasives, 2020).
L. camara has become invasive due to its ability to out compete the indigenous plant species in the area by forming dense clumps which suppress and interrupt the growth and regeneration of indigenous plant species (Invasives, 2020). The L. camara disperses its seed through wind and mechanical means.

Eucalyptus spp.
Eucalyptus spp. or commonly known as Gum species are native to Australia (Witt, 2020). Eucalyptus spp. are tall tree species which are evergreen (WoodlandTrust, 2019). These trees can grow to heights of 90m.
The Eucalyptus spp. can be identified by the shedding of bark that occurs on the trunk of the tree; the leaves have a leathery texture and tend to hang obliquely or vertically on the tree; the flowers form a cap like structure; and the fruit is a capsule surrounded by a woody cup shaped receptacle and inside the fruit are many minute seeds (Britannica, 2023).
Eucalyptus spp. have become invasive in KwaZulu Natal and many other provinces by their ability to release chemicals in the soil surrounding their root structure, which in turn alters the soil chemistry, that inhibits the growth of other indigenous plants which decreases competition for the Eucalyptus spp. (UCT, 2018). The Eucalyptus spp. disperses its seed through primarily wind and water (Queensland, 2014).

Solanum mauritianum
Solanum mauritianum or commonly known as Bugweed is native to South America (Invasives, 2020). S. mauritianum are shrub or short tree plants that can grow as high as 4m (Invasives, 2020).
S. mauritianum is identified by whitish hairs covering the plants; the leaves are dull green in colour and are velvety on top and whiteish underneath; the leaves release a strong smell when crushed or bruised; the flowers are in compact clusters and purple in colour; and the fruits are small berries that are green and turn yellow when they ripen (Invasives, 2020).
The S. mauritianum has become invasive due to its ability to outcompete and replace indigenous plants, and it is avoided by grazers due to the hairs on the leaves and stems causing allergic reactions in the throat and the fruit are poisonous (Invasives, 2020). The seeds of S. mauritianum are dispersed by wind and mechanical means (Campbell & van Staden, 1983).

ENVASS boasts a highly proficient and seasoned Compliance Monitoring, ECO, and Specialist Team.Our Specialist Team has extensive experience in Invasive Management Plans and are always willing to assist. Our team possesses extensive expertise in local legislation and compliance monitoring, ECO, and specialist works, ensuring the seamless fulfilment of your specific compliance monitoring, ECO and specialist needs.

BioNET-EAFRINET, 2020. Chromolaena odorata (Chromolaena). [Online]
Available at: https://keys.lucidcentral.org/keys/v3/eafrinet/weeds/key/weeds/Media/Html/Chromolaena_odorata_(Chromolaena).htm
[Accessed 12 October 2023].

Britannica, 2023. eucalyptus. [Online]
Available at: https://www.britannica.com/plant/Eucalyptus
[Accessed 13 October 2023].

Campbell, P. & van Staden, J., 1983. Germination of seeds of Solanum mauritianum. South African Journal of Botany, 2(4), pp. 301-304.

Invasives, 2020. Bugweed. [Online]
Available at: https://invasives.org.za/fact-sheet/bugweed/
[Accessed 13 October 2023].

Invasives, 2020. Lantana. [Online]
[Accessed 12 October 2023].

Meijninger, W. & Jarmain, C., 2014. Satellite-based annual evaporation estimates of invasive alien plant species and native vegetation in South Africa. Water SA, 40(1), p. 95.

Queensland, 2014. Eucalypt open-forests management guide - Ecology. [Online]
Available at: https://www.qld.gov.au/environment/plants-animals/habitats/regrowth/regrowth-guides/euc-open/euc-open-ecology#:~:text=The%20biology%20of%20open%2Dforest%20eucalypts&text=The%20seed%20of%20most%20open,ongoing%20when%20seed%20is%20available.
[Accessed 13 October 2023].

Rojas-Sandoval, J. & Pasiecznik, N., 2015. Acacia mearnsii (black wattle). CABI.

UCT, 2018. Invasive alien plants in South Africa pose huge risks, but they can be stopped. [Online]
Available at: https://www.news.uct.ac.za/article/-2018-04-19-invasive-alien-plants-in-south-africa-pose-huge-risks-but-they-can-be-stopped
[Accessed 13 October 2023].

Witt, A., 2020. Eucalyptus – the ‘thirsty’ trees threatening to ‘drink’ South Africa dry. CABI - Invasives Blog, 21 January.

WoodlandTrust, 2019. EUCALYPTUS. [Online]
Available at: https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/british-trees/a-z-of-british-trees/eucalyptus/
[Accessed 13 October 2023].

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