What is an Invasive Alien Plant?
An invasive alien plant (IAP) is a species introduced either accidentally or intentionally by humans and allowed to grow outside its natural habitat. When invasive vegetation prevents natural, indigenous plant growth, it threatens biological diversity. These plants are not native to the ecosystem and can cause economic or environmental harm. Sometimes the harm is not immediately apparent and is only noticed once the alien plants start causing problems in their new homes. In the Eastern Cape of South Africa, several IAPs have become particularly problematic.
Here are some of the most invasive alien plants in the region:
Inkberry (Gallberry - Cestrum laevigatum) is a slow-growing, upright-rounded, broadleaf evergreen shrub from the holly family. It is native to eastern North America. It typically matures to 1,5 to 2,4 metres tall and can spread by root suckers to form colonies. Inkberry has leathery, olive green leaves and small, usually black berries. It is multi-stemmed with small trumpet-like flowers in a cluster.
Inkberry Gallery
The Brazilian Pepper (Schinus terebinthifolius) is an evergreen shrub or tree that can reach heights up to 6 meters. The tree is characterised by its wide-spreading, horizontal branches. Its leaves are a dark green with distinct pale veins on the top side, becoming paler and smoother underneath. The compound leaves consist of 3 to 4 pairs of side leaflets and a single terminal leaflet. It bears bright red, slightly fleshy berries known as drupes. Each berry contains one poisonous seed. Creamy-white flowers appear from September to March, with male and female blooms on separate trees. Exposure to the sap may irritate the skin and impact the respiratory tract.
Brazilian Pepper Gallery
Lantana (Lantana camara) is a shrub characterised by small, attractive clusters of multicoloured flowers, typically ranging from red, orange, and yellow to pink and purple. It has sprawling branches with thorny stems. The seedlings can be identified by their duller green leaves compared to indigenous bramble. Originally introduced to South Africa as an ornamental plant, it has become invasive, creating dense thickets that displace native species and alter habitats.
Lantana Gallery
The Port Jackson willow (Acacia saligna) is characterised by long leaves with a distinct central vein and multiple feather-like side veins visible when backlit. This evergreen tree reaches heights of 3-7 meters and has leaves that transition from blue-green to bright green. Its bright yellow, globe-shaped flowers blossom from August to November, followed by brown pods edged with hardened, whitish margins.
Port Jackson Willow Gallery
The Long-leaved wattle (Acacia longifolia) has elongated bright green leaves marked by prominent longitudinal veins. The leaves are typically about half the size of the Port Jackson willow. It features two distinct veins originating from the base of the leaf, along with several other veins that start from the same point. This species has a shallow root system lacking a taproot, making it easier to remove, particularly in soft soil. The Long-leaved wattle is a perennial shrub or spreading tree that grows 2-6 meters high. Its flowers are bright yellow and cylindrical, measuring up to 50mm in length and 7mm in width, blooming from July to September. Native to Australia and Tasmania, the Long-leaved wattle was introduced to South Africa for dune stabilisation and has proliferated along the coast, outcompeting and displacing native species.
Long-leaved Wattle Gallery
Rooikrans (Acacia cyclops) have three prominent veins starting at the base, along with multiple other faint veins originating from the base. It features a curved seed pod with a seed that resembles an eye. Rooikrans is also commonly known as coastal wattle, cyclops wattle, one-eyed wattle, red-eyed wattle, red wreath acacia, western coastal wattle, rooikrans acacia, is a coastal shrub or small tree in the family Fabaceae.
Rooikrans Gallery
The Gum Tree (Eucalyptus species variety) can be easily identified by crushing and smelling its leaves. Eucalyptus mannifera, also known as the brittle gum or red spotted gum, is a small to medium-sized tree species native to southeastern Australia.
Gum Tree Gallery
A Pine Tree (Pinus species) is any coniferous tree or shrub belonging to the genus Pinus within the family Pinaceae. Pinus is the only genus in the subfamily Pinoideae. According to World Flora Online, there are 187 currently accepted species names of pines, along with additional synonyms, which makes it the largest genus within the conifers. They are characterised by their needle-like leaves.
Pine Tree Gallery
Water Hyacinth (Eichhornia crassipes) is a free-floating aquatic plant distinguished by its thick, waxy leaves and striking lavender flowers. It was introduced as an ornamental species for ponds and has become a major problem in waterways, where it forms dense mats that reduce water flow and oxygen levels, affecting aquatic life.
Water Hyacinth Gallery
Famine Weed (Campuloclinium macrocephalums): This weed has lobed leaves and small white flowers. It’s thought to have been introduced accidentally through contaminated grain shipments. Famine weed can cause allergic reactions in humans and animals and threatens crop yields due to its rapid spread and ability to dominate fields.
Famine Weed Gallery
Bugweed (Solanum mauritianum): This shrub has soft, velvety leaves and clusters of purple flowers followed by yellow berries. Bug weed was likely introduced from South America for its potential as a quick-growing hedge. It’s now widespread, shading out native plants and disrupting ecosystems.
Bugweed Gallery
Pompom Weed (Campuloclinium macrocephalum): This plant is easily identifiable by its fluffy, pink-purple flowers resembling cheerleader pompoms. It’s a Category 1b invasive species, which means it must be controlled by law. Due to its attractive flowers, pompom weed was likely introduced as an ornamental plant but has since spread aggressively, outcompeting native vegetation.
Pompom Weed Gallery
Why Should These Alien Shrubs be Removed?
The removal of these invasive alien plants is crucial for several reasons. They often consume more water than native species, exacerbating water scarcity. They can also fuel wildfires, reduce biodiversity, and impact agriculture by competing with crops for resources. Controlling these species helps preserve the Eastern Cape's unique ecosystems, which are home to many endemic species and support local livelihoods. Effective management and removal of IAPs are essential for maintaining the ecological balance and ensuring the sustainability of natural resources in the region.
Sources
Invasive alien plants in South Africa pose huge risks, but they can be stopped (theconversation.com)
https://safacts.co.za/list-of-alien-invasive-plants-in-south-africa/
All images provided by AI
Mr Mervyn Brouard
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