Honey locust is a multi-use tree used in erosion control, fodder and fuel. It was planted extensively around farms for its uses, especially in natural grasslands which had few trees for wood or fodder. It is now a serious pest and habitat transformer.
It can often be overlooked for one of our indigenous acacia species and therefore not readily identified as a serious invader. It is prevalent across the Free State, Gauteng, North West and Mpumalanga where other invaders such as black and green wattle thrive.
Montpellier broom naturally occurs around the Mediterranean of Europe and North Africa. The winter rainfall and climate of Cape Town suits this shrub and it has become a problematic plant in the Western Cape.
The spread of this shrub must be contained, and sightings reported to the City of Cape Town Invasive Species Unit. This shrub is in the family Fabaceae…a massive family with numerus invasive species such as the Australian wattle. They produce copious numbers of seeds within seed pods and these are easily dispersed by wind, rainwater and animals.
This shrub-like euphorbia has escaped from gardens and found regularly in natural areas around Durban in KwaZulu-Natal. It has the potential to become a problematic invader.
White poinsettia is now controlled by regulations and further growing or selling of this shrub is strictly prohibited.
Cacti are popular garden ornamentals due to their hardiness, requiring minimal water, and their often bright and showy flowers. However, many cactus species have become highly invasive across Africa and cause considerable economic damage. Their sharp spines often injure wildlife and grazing livestock. Some farmers have been forced to vacate land which has become overgrown with cactus.
The imbricate cactus is widespread in South Africa. Fortunately, a biocontrol agent called Dactylopius tomentosus (imbricata biotype) is effective in controlling this cactus. Biocontrol is used extensively on many different invasive cacti. This is particularly effective in nature reserves and national parks where mechanical control is difficult and the use of herbicides is to be avoided. There is also a National Invasive Cactus Working Group that coordinates efforts to manage cactus invasions. They meet biannually.
The canary-bird bush or bird flower is an ornamental plant which was introduced from East Africa. It has jumped the garden fence and the seeds are easily dispersed along grasslands. It is relatively common in open grasslands and fields across Gauteng and Mpumalanga.
The bright yellow flowers bloom throughout summer and are most characteristic. When viewed from a certain angle they resemble small yellow birds, hence the common name of this evergreen shrub.
Cotoneasters originate from cool mountainous regions of Asia such as the Himalayas and China. They are resistant to frost and therefore thrive in the high-altitude grasslands of South Africa. These hardy plants pose a serious threat to our natural grassland ecosystems in the mountainous region around Lesotho, the Free State and KwaZulu-Natal.
Professor Martin Grant and colleagues from Rhodes University are investigating the ecology of high-altitude grassland invader such as the cotoneasters and the similar fire-thorns (Pyracantha).
The nodding thistle is a recently identified invader which appears to be confined to the Eastern Cape, from Gqberha (Port Elizabeth) through East London to Cape St Francis. It invades grasslands, roadsides and pastures.
Nodding thistle superficially resembles the more widespread and common spear thistle but has a different flower form.
There are many species and varieties of canna which are popular as garden ornamentals. It is a perennial herb with rhizomatous roots. It is famous for its ability to rapidly spread along well-watered gardens, and they are often chopped out and dumped in landfills or open spaces. From here they rapidly take root and spread along streams and drainage lines.
The small black seeds were used as musket ammunition and hence this plant coined the name Indian shot. This plant is widespread along coastal regions in KwaZulu-Natal and the Eastern Cape, but also prevalent in peri-urban regions of Gauteng.
Under NEMBA AIS regulations this climbing plant is known as Aristolochia elegans, but was recently identified as Aristolichia littoralis. It is a twining climber that clambers up and over shrubs and trees, along fences and up buildings. It is an evergreen plant with large leaves. These leaves block out essential sunlight leading to the host plant being weakened or eventually dying.
Dutchman’s pipe favours tropical and Afromontane forests in KwaZulu-Natal, Mpumalanga and Limpopo. A characteristic feature is the large, heart-shaped maroon flowers.
The mud plantain has uncertain origins but suspected to have arrived from the northern hemisphere. It requires moist or damp places to grow. It is an aquatic herb with large penetrating roots, making it difficult to pull out.
Mud plantain is relatively widespread across South Africa and can be found in and around wetlands in most provinces.