Some of the most common plants in South African gardens are actually dangerous invaders. These invasive alien plants in South Africa may appear beautiful, but they harm local ecosystems, displace indigenous plants, and break environmental laws.
Many homeowners unknowingly cultivate these non-native species, unaware of their negative impact on biodiversity and water resources. If left unchecked, they spread aggressively, choking out indigenous plant life and altering entire ecosystems.
This guide highlights 10 of the worst invasive alien plants in South Africa and provides eco-friendly alternatives to replace them. Additionally, we’ll explore other widespread alien plants commonly found in gardens that should also be removed.
What Are Invasive Alien Plants & Why Are They a Problem?
Definition:
Invasive alien plants (IAPs) in South Africa are non-native species that have been introduced intentionally or accidentally. Due to their fast growth and aggressive spread, they outcompete indigenous plants, threatening local biodiversity.
Why Are They Harmful?
- Reduce Indigenous Plant Diversity – Many alien species overtake native plants, altering habitats.
- Destroy Wildlife Habitats – They impact food sources, nesting sites, and soil health.
- Increase Water Consumption – Some species deplete water sources, worsening South Africa’s water crisis.
- Highly Flammable & Increase Fire Risk – Many dry out quickly, fueling dangerous wildfires.
- Legally Prohibited – Several Category 1 plants must be removed by law.
Solution: The best way to protect local ecosystems is to identify, remove, and replace invasive alien plants with indigenous alternatives.
10 Common Invasive Alien Plants in South Africa
1. Billygoat Weed & Mexican Ageratum
Looks Like: A soft, hairy-leaved plant with mauve, blue, pink, or white fluffy flowers blooming year-round.
Category: 1 (Illegal in SA)
Found In: Eastern Cape, KwaZulu-Natal, Limpopo, Mpumalanga
Why It’s a Problem:
- Spreads rapidly year-round by producing thousands of seeds.
- Highly toxic to humans and pets.
- Displaces indigenous wildflowers, reducing plant diversity.
Other facts: One needs to note that this plant’s hybridised forms are available nowadays. Thanks to agricultural science, hybrids are sterile and do not produce seeds. Ageratum is a good mosquito repellent when grown in the garden. Furthermore, it has insecticidal and nematicidal (nematodes) properties.
Eco-Friendly Alternatives: Scabiosa ‘Butterfly Blue,’ Felicia ‘Glenwood,’ or sterile Ageratums.
2. Mother of Millions (Chandelier Plant)
Looks Like: A Madagascan succulent with spotted, pencil-shaped leaves and bright orange to magenta flowers.
Category: 1 (Illegal in SA)
Found In: Gauteng, KwaZulu-Natal, Limpopo, Mpumalanga
Why It’s a Problem:
- Produces thousands of small plantlets, spreading aggressively.
- Toxic to livestock and pets.
- Outcompetes indigenous rocky outcrop vegetation.
Eco-Friendly Alternatives: Cotyledon flanaganii, Aloe cooperii, Senecio ficoides.
3. Indian Shot (Canna Lily)
Looks Like: A tropical flowering plant with large green or bronze-purple leaves and red/orange flowers.
Category: 1 (Illegal in SA)
Found In: KwaZulu-Natal, Gauteng, Eastern & Western Cape, Mpumalanga, Limpopo
Why It’s a Problem:
- Spreads aggressively via seeds and underground rhizomes.
- Forms dense clumps, outcompeting local plants.
- Consumes large amounts of water, harming wetlands.
Other facts: People often use the hard black seeds of this plant for jewellery making and for rattles in some musical instruments. It is also used to make purple dye. The rhizomes of this canna are edible when cooked and are even medicinal. You can even make paper from the leaves of this plant. We are not encouraging you to keep Canna Lillies in your garden by stating all these interesting facts. We say you can use their parts when removing the invasive Canna plants. Many non-invasive Canna hybrids exist, which are actually a lot more ornamental.
Eco-Friendly Alternatives: Wachendorfia thyrsiflora, Zantedeschia aethiopica, or non-invasive Canna hybrids.
4. Blue Echium (Blueweed)
Looks Like: A 1m-tall biennial covered in coarse white hairs, with blue or purple flowers blooming October-April.
Category: 1 (Illegal in SA)
Found In: Western Cape, Free State, Gauteng
Why It’s a Problem:
- Spreads rapidly, invading farmlands, pastures, and roadsides.
- Toxic & skin-irritating to humans and animals.
Other facts: People often add the flowers of this plant, to salads, crystallise it, or make it into a cordial. Furthermore, they often use the roots of this plant to make a red dye. When working with this plant, remember to wear gloves, as the hairs on this plant can hurt you and are a skin irritant.
Eco-Friendly Alternatives: Limonium perezii, Aristea ecklonii, Lobostemon fruticosus.
5. Morning Glory (Common & Perennial)
Looks Like: A climbing vine with heart-shaped leaves and purple-blue or magenta funnel-shaped flowers.
Category: 1 & 3 (Illegal in some provinces)
Found In: KwaZulu-Natal, Gauteng, Mpumalanga, Limpopo, Eastern & Western Cape
Why It’s a Problem:
- Forms dense growth, choking trees and shrubs.
- Spreads rapidly via fine seeds.
Eco-Friendly Alternatives: Thunbergia grandiflora, Petrea volubilis, Wisteria sinensis.
6. Tick Berry (Lantana)
Looks Like: A 2m-tall shrub with rough, scented leaves and flat-topped flower clusters in pink, red, orange, or yellow.
Category: 1 (Illegal in SA)
Found In: Western Cape, Eastern Cape, KwaZulu-Natal, Mpumalanga, Limpopo, North West
Why It’s a Problem:
- Birds spread the seeds, making it hard to control.
- Poisonous to livestock and humans.
Other facts: This plant has become so invasive mainly due to humans who plant them in their gardens. As soon as it produces seed, this plant can ‘escape’ via seed dispersal. Some people claim to have cultivated sterile flower varieties. Unfortunately, we cannot always trust these varieties. Years ago, a pure yellow form brought out was meant to be sterile, but it eventually became invasive. Lantana leaves are very medicinal. Some crafty people use the plant’s stems to make furniture.
Eco-Friendly Alternatives: Polygala fruticosa, Orphium frutescens, Verbena hybrids.
7. St Joseph’s Lily (Trumpet Lily)
Looks Like: A 2m-tall bulbous plant with shiny narrow leaves and large, fragrant white flowers.
Category: 1 (Illegal in SA)
Found In: Eastern Cape, KwaZulu-Natal, Gauteng, Mpumalanga, Limpopo
Why It’s a Problem:
Invasive in wetlands and grasslands.
Spreads via seeds and bulbs, forming dense clumps.
Other facts: A fascinating fact is that the plant’s bulb is very much edible, and it can be cooked and eaten like a potato. It is very rich in starch.
Eco-Friendly Alternatives: Amaryllis belladona, Zantedeschia aethiopica, non-invasive lily hybrids.
8. Four o’clock plant
Looks Like: A bushy shrub with fragrant tubular flowers that open in the evening.
Category: 1 (Illegal in SA)
Found In: Gauteng, Limpopo, Mpumalanga, North West
Why It’s a Problem:
- Takes over dry sandy areas.
- Spreads easily via seeds.
Other facts: This is a rather confusing plant as people have varying opinions on what to use this plant for. Some people say it is edible to a certain extent and that they can make red dye from the flowers. Popular opinion is that one can use the dye for food colouring. On the other hand, some people say it is poisonous. One confirmed use is that you can use the red dye made from the flowers for dying fabrics.
Eco-Friendly Alternatives: Azalea hybrids, Cistus species, Pentas lanceolata.
9. Oleander
Looks Like: A tall evergreen shrub with dark green leaves and pink, red, or white flowers.
Category: 1 (Illegal in SA)
Found In: Eastern & Western Cape, KwaZulu-Natal, Mpumalanga
Why It’s a Problem:
- Spreads aggressively via wind-dispersed seeds.
- Highly toxic to humans and animals.
Other facts: Oleander is a medicinal plant, although one of the world’s most toxic plants. It is best to leave the plant’s medicinal use to the professionals who know how to work with it! Not only is Oleander poisonous when consumed, but it will also highly irritate your skin if you come into contact with the milky sap. Furthermore, when it burns, it releases toxic fumes.
Eco-Friendly Alternatives: Bauhinia galpinii, Escallonia ‘Pink’, Rhaphiolepis indica ‘Pink’.
10. Wandering Jew
Looks Like: A ground-cover creeper with bluish-green leaves with silver bands.
Category: 1 (Illegal in SA)
Found In: Eastern Cape, but can spread elsewhere.
Why It’s a Problem:
- Causes skin irritation in pets and humans.
- Spreads aggressively via stems and roots.
Other facts: The plant has medicinal properties, but is only to be used by those that know what they are doing.
Eco-Friendly Alternatives: Crassula multicava, Tradescantia virginiana hybrids, Ajuga reptans.
Other Common Invasive Alien Plants in South African Gardens
Beyond the Category 1 invaders we’ve covered, there are many other non-native plants thriving in South African gardens. While these species may not be as aggressively harmful, they still disrupt local ecosystems, spread uncontrollably, and threaten indigenous biodiversity.
Here are some of the most common invasive plants found in gardens across South Africa:
1. Syringa (Melia azedarach) – Persian Lilac
- Why It’s a Problem: This fast-growing shade tree produces clusters of purple flowers followed by highly toxic yellow berries, which birds spread. It outcompetes native trees in urban areas.
- Better Alternative: Buddleja saligna (False Olive), Halleria lucida (Tree Fuchsia).
2. Sword Fern (Nephrolepis exaltata) – Wild Boston Fern
- Why It’s a Problem: A popular ornamental fern that spreads through creeping rhizomes, forming dense carpets that choke indigenous undergrowth.
- Better Alternative: Blechnum capense, Asparagus virgatus.
3. Australian Black Wattle (Acacia mearnsii)
- Why It’s a Problem: An extremely invasive tree that consumes vast amounts of water, reducing groundwater availability for native plants. It also increases fire risks.
- Better Alternative: Virgilia divaricata (Keurboom), Acacia karroo (Sweet Thorn).
4. Jacaranda (Jacaranda mimosifolia)
- Why It’s a Problem: Despite its beauty, this tree is an invasive water-hungry species that spreads rapidly through seed dispersal, particularly in Gauteng and Pretoria.
- Better Alternative: Dombeya rotundifolia (Wild Pear), Bolusanthus speciosus (Tree Wisteria).
5. Pampas Grass (Cortaderia selloana)
- Why It’s a Problem: A fast-spreading ornamental grass that invades wetlands and grasslands, outcompeting native grasses.
- Better Alternative: Aristida junciformis (Ngongoni Three-Awn), Miscanthus capensis.
6. Bugweed (Solanum mauritianum)
- Why It’s a Problem: Produces millions of seeds that birds spread widely, forming dense thickets that smother indigenous plants. It’s also toxic to livestock.
- Better Alternative: Buddleja salviifolia (Sagewood), Buddleja auriculata.
7. Mexican Fan Palm (Washingtonia robusta)
- Why It’s a Problem: This palm species spreads aggressively along riverbanks, competing with indigenous palms and altering wetland ecosystems.
- Better Alternative: Hyphaene coriacea (Ilala Palm), Phoenix reclinata (Wild Date Palm).
Why You Should Remove These Plants Too
Even though these plants may not be classified as highly invasive (Category 1), they still harm local ecosystems by:
- Outcompeting indigenous plants for sunlight, nutrients, and water.
- Altering soil composition, making it harder for native species to thrive.
- Disrupting natural water cycles, contributing to drought conditions.
- Providing poor food sources for local wildlife, affecting biodiversity.
What You Can Do:
- Identify if you have these species in your garden.
- Gradually replace them with indigenous alternatives.
- Avoid buying or planting invasive species when landscaping.
- Seek expert help to remove and replace these plants safely.
Final Thoughts
Many gardeners unknowingly harbour illegal and harmful invasive species in their gardens. While these plants may be beautiful, they threaten South Africa’s biodiversity and ecosystems.
By choosing indigenous, non-invasive plants, you can create a stunning garden that benefits the environment and local wildlife.
