| Article Index |
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| All you need to know about Invasive Alien Plants |
| 2. The trouble they cause |
| 3. The laws against invasive alien plants |
| 4. Who is fighting the weeds? |
| 5. What can the public do? |
| All Pages |
All you need to know about invasive Alien Plants.
1. What are invasive alien plants?
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WeedBuster Week is an annual event in South Africa which runs from 5-11 October this year. Its aim is to let everyone know what invasive alien plants are, the extent of the problems they cause and how we can combat them.
Why are we holding WeedBuster Week?
Invading alien plants (IAPs) are the single biggest threat to plant and animal biodiversity in South Africa. The cost of controlling IAPs in South Africa is estimated at R600 million a year over the next 20 years.
Did you know?
Alien invasive plants (IAPs) have invaded 10 million hectares of South Africa or an area the size of KwaZulu-Natal). This is 10% of our available land. Invasive alien plants in South Africa use 7% of our water...which is about the same amount of water needed by humans to survive in SA.
IAPs cause major damage to ecosystems by crowding out key species and thereby threaten the biodiversity which attracts tourists to our country. IAPs also reduce our ability to farm; intensify flooding and fires; cause erosion, destruction of rivers, siltation of dams and estuaries, and poor water quality and can cause a mass extinction of indigenous plants and animals. Aquatic invaders cover dams and lakes and block rivers. If IAPs are left uncontrolled, the problem will double within 15 years.
What is an invasive alien plant (IAP)?
There are 27 000 indigenous plant species in the country and 9000 exotic or alien species in South Africa (ie plants that came from foreign lands).Only 198 of the 9000 foreign plant species in South Africa are deemed to be problem invader aliens - or ‘bad' plants.
IAPs are plants that have been introduced from other countries and out-compete the indigenous species. They are highly adaptable and don't have the natural enemies they would have back home. They easily invade many ecological niches in their new homes, from rivers to mountain kloofs.
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They grow fast and produce enormous amounts of seed. Or they have deep or spreading root systems that are difficult to remove. This helps them to multiply quickly and crowd out local plants. Because of the way they grow, and if we do nothing about the spread of IAPs, the land they occupy could double in the next 15 years.
What are some of the culprits? Their common names are wattle, lantana, bugweed, pampas grass, syringa, Port Jackson, rooikrans and gum trees. In the water, invader aquatics include water hyacinth, water lettuce and parrot's feather. These trees are commonly seen in gardens and in the veld and therein lies the problem.
2. The trouble they cause
Invasive alien plants (IAPs) manage to spread so fast by growing very quickly, producing lots of seeds or having tough invasive root systems.
What damage do they cause?
- They invade land and have covered nearly 8% of South Africa and if we do nothing about the spread of IAPs, the land they occupy could double in the next 15 years.
- They waste water: We lose more than 7% of all water run off to 198 invasive alien plants.
- They threaten biodiversity: Invasive alien plants displace the more delicate and slow growing indigenous plants especially in the Cape Floral Kingdom, one of the world's biodiversity hotspots with some 8 600 species of which 70% occur nowhere else on the planet.
And this is not the only ecosystem under threat; aliens are found along rivers in Mpumalanga, in Northern Province, in kloofs in KwaZulu-Natal, and even in the arid areas of the Northern Cape. These are all areas tourists commonly visit. Biodiversity is one of South Africa's key tourist attractions and earns billions of rands in foreign exchange each year. IAPs could threaten this industry.
IAPs such as the pompom weed are invading grasslands - taking up productive land that could be better used for crops and livestock grazing. In South Africa, IAPs can smother and kill trees, hamper forestry operations, crowd out sweet grazing grass and fatally poison cattle which graze on them in times of drought.
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- They cause run away fires and erosion
Many of invasive trees are ‘born to burn' using fire to germinate seeds in huge numbers afterwards. After fires, and before plants have re-established themselves on burnt ground, invasive aliens leave large patches of bare ground which are vulnerable to erosion. This silts up dams and estuaries and results in poor water quality. - Many are toxic to humans and livestock
Tickberry (Lantana camara) is just one of many invaders that is toxic to livestock, resulting in large financial losses to farmers. Common plants such as oleanders, syringas, privets and morning glories are toxic to humans and often eaten by children. - They take over dams, lakes and rivers
Water hyacinth has taken over the Benoni Lakes system, water sports at Roodeplaat Dam, north east of Pretoria have come to a grinding halt, and continually clearing the Mzunduzi of water hyacinth near Pietermaritzburg costs millions in taxpayers money each year. Hydrilla, a submerged aquatic invader has taken over 800 hectares of the Pongolapoort Dam, northern KZN. - They are difficult and expensive to eradicate
Many are able to evolve constantly - and expensive to remove.
Did you know?
South Africa has spent R400 million a year for the past 15 years attempting to control invasive alien plants and is needing R600 million a year to continue the fight for the next 20 years.
3. The laws against invasive alien plants
Huge losses are caused by alien invasive plants (IAPs): the amount of water they consume, the amount of productive land they cover, the fires they cause and loss of biodiversity, to name just a few. It makes sense then that these destructive plants have been declared illegal. As the legislation stands today, 198 plants are declared alien invaders (under the Conservation of Agricultural Resources Act, 2001).
These invaders are divided into three categories.
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- Category 1 - Remove and Destroy
Category 1 Plants are those that may no longer be grown or planted and must be removed and destroyed. Examples include lantana, pom pom weed, bugweed, azolla, queen of the night cactus, pampas grass, cat's claw creeper, red sesbania, yellow oleander, yellow bells and water hyacinth.
- Category 2 - Need a permit to grow in suburban gardens
Category 2 plants (invader plants of commercial value) can only be grown with a permit (obtainable from one of the regional offices of the National Agricultural Dept) in public spaces such as parks, schools and hospitals. Examples include black wattle, patula pine, sisal, red eye, grey poplar, watercress, Port Jackson willow, guava, cluster pine, honey locust and weeping willow (not be confused with the indigenous willows).
- Category 3 - No planting. No selling.
Category 3 plants (invader plants used as ornamentals) can no longer be planted or sold by nurseries, but may remain in your garden if kept under control. Examples include jacaranda (excluding the sterile variety), seringa, Australian silky oak, cotoneaster, Formosa lily, sword fern, tipuana tree and New Zealand Christmas tree
What happens if you are found with one of these plants on your land?
You may be visited by a weed inspector from the National Department of Agriculture or your local council and issued with directive to remove an illegal plant or obtain a permit for it. If you fail to comply after a reasonable time, prosecution follows and on being found guilty, the penalty can be two years in prison or R10 000, or both.
In reality, there are only 19 inspectors to police the whole of South Africa, so it may take a while before you are caught. In the meantime it's up to all of us to take responsibility for the weeds on our properties and get rid of them. Remember, each weed you leave standing will produce hundreds more and this means more damage to the enviroment. It is also our legal duty to eradicate the weeds on our land. In our next slot we will look at who is fighting IAPs in South Africa.
4. Who is fighting the weeds?
Who is fighting the problem and what you can do?
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In South Africa, the fight against aliens has been spearheaded by the Department of Water and Environmental Affairs's - Working for Water (WfW) Programme set up in 1995. Its main aim is to clear IAPs from priority catchments to release more water for productive uses.
This programme works in partnership with local communities, to whom it provides jobs, and also with national government departments including the Department of Agriculture, KZN Invasive Alien Species Programme, provincial departments of agriculture, conservation and environment, research foundations and private companies. WFW also have partnerships with the green industries, pet trade and forestry sector.
Planting good plants vs bad plants
In August 2009, the WFW Nurseries Partnership Programme launched Plant Me Instead campaign in 150 garden centres across South Africa. The aim is to educate gardeners to remove ‘bad' plants and replace them with ‘good' plants.
Weedbuster Week National Event - Bloemhof Dam
WeedBuster Week has been held for the past nine years in South Africa to highlight the challenge of IAPs. This year's National WeedBuster Week event will be held at the Bloemhof Dam, where WFW is actively involved in attempting to prevent invasive aquatic weeds such as water hyacinth (which is already taking over the Vaal River) from reaching the Orange River.
Did you know?
Because invasive species are such a problem all over the world, a Global Invasive Species Programme (GISP) was first set up in Los Angeles in 1998 to control the movement of alien species and 50 countries (including South Africa).
5. What can the public do?
What you and I ...do.
IAPs grow quickly which makes them very popular garden plants. Old habits and favourites die hard. There was a big outcry when Carte Blanche announced that 70 000 jacarandas to be cut down in Pretoria as an April Fools Joke a few years ago.
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Happily for its fans, the jacaranda is a category 3 plant and does not need be uprooted. However, as a gardener, you've got to be tough and wean yourself off those ‘grow-like-weeds' IAPs since you are responsible for what grows on your land.
- Learn to identify IAPs
The first thing to do is to get a list of the worst offenders. For a copy of the alien invader plant list, call 0800-005-376 or download a list from www.lifeisagarden.co.za - Look out for pictures of IAPs
Then you may need some help in identifying the plants. See pictures of invasive alien plants at www.agis.agric.za/agisweb/wip. - Remove IAPs
Next you need information on eradicating aliens. This normally involves a combination of:
1) Mechanical felling, weeding by hand and controlled burning.
2) Chemical killing with environmentally safe herbicides.
Obtain advice on treatment methods by contacting the Working for Water WeedBuster toll free line 0800 005 376 or visit the DWAF website on http://www.dwaf.gov.za/wfw or contact 011 723 9000 (WFW Nurseries Partnership Programme).
It's darn hard work getting rid of invaders
To get rid of IAPs successfully you need three steps:
- Initial control: drastic reduction of existing population
- Follow-up control: control of seedlings, root suckers and coppice growth
- Maintenance control: sustain low alien plant numbers with annual control
Aliens cost money
Declared weeds and invader plants are one of the most significant drivers of environmental changes worldwide. The American government estimates that invasive species account for 4% of the global Gross Domestic Product.
They contribute to social instability and economic hardship, placing constraints on sustainable development, economic growth and environmental conservation. The direct costs of weeds to a single country can amount to billions of dollars annually. Invasives could cost the American economy at least US$24 billion per annum in reductions in water run-off, biodiversity loss, ecosystem resilience, loss of productive land, increased costs of fire protection and erosion following fires.
It is estimated that alien invasions may have reduced the value of fynbos ecosystems by US$11,75 billion. The cost to clear plant invasions in South Africa could amount to US1,2 billion. South Africa spends R600 million a year removing invasive alien plants.
4. Plant good plants - Plant Me Instead
Having removed invasive alien plants from your garden, replace them with good plants. There are 27 000 indigenous plants in the country and 9000 exotic or alien plants in the country. Only 198 of the 9000 foreigners are deemed to be bad invaders. The Plant Me Instead Campaign in 150 garden centres nationwide offers information on the range of good plants available for ecologically minded gardeners to plant in their gardens. See www.lifeisagarden.co.za
FACTS ABOUT INVASIVE ALIEN PLANTS
- Did you know that New Zealand's Airport Control for Invasive Alien Species has twenty inspectors, stringent laws and harsh penalties for anyone bringing foreign plants or animals into the country?
- Did you know that Britain regards its outbreak of foot and mouth disease as an invasive alien virus which cost the UK tourism, trade and agriculture sectors over R135 billion (12,5 billion pounds).
- Did you know? Our indigenous flora is causing havoc in Australia! Our own indigenous watsonia, arum, gazania and agapanthus are regarded as invader alien weeds in Australia. Watsonias are a huge problem in Melbourne. Gazanias are a problem in Perth.
What happens if we do nothing?
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If South Africa takes no action it is estimated that alien infestations will double in the next 15 years.
What else can you do to help?
If you own land, keep it clear of invasive alien plants.
- Do not buy invasive alien plants from nurseries, and do not support nurseries that sell such plants.
- Join a volunteer clearing or hack group
- Buy firewood, charcoal, crafts, furniture, toys, building material, mulch, etc made from invasive alien plants.
- Do not bring foreign plants and animals into our country or transplant them from other parts of our country - and do not send ours to other countries
- Inform authorities about landowners who are causing the spread of invasive alien plants.
- Encourage your local authority, agricultural union, school, community, etc to work with the Working for Water programme.
WfW toll free line 0800 005 376 or visit the DWAF website on http://www.dwaf.gov.za/wfw
Some poisonous garden ‘companions'
- The South American lantana (Lantana camara - category 1) is regarded as one of the world's ten worst weeds and occurs in 2,2 million hectares across South Africa. The green fruits are highly toxic and child fatalities have been recorded.
- The syringa (Melia azedarach - category 3) occurs in three million hectares of land across South Africa. The berries are highly toxic and fatalities have been reported.
- The small black seeds of the castor oil plant (Ricinus communis - category 2) are extremely toxic. One seed is enough to kill a child.
Invasive alien aquatic plants
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Actively thriving colonies of water hyacinth may double their numbers every 11 to 18 days. Kariba Weed grows at an alarming rate - in two years it spread from 20 hectares to 40 000 hectares in the Kariba Dam.
- Roodeplaat Dam - North East of Pretoria: 70% of the dam is covered in a thick mat of water hyacinth endanging schools rowing.
- Benoni Lakes - the four Benoni lakes have been invaded by water hyacinth endangering leisure yachting.
- Roodekopjes Dam - north west of Brits and the centre of the bass leisure fishing industry is 20% covered in water hyacinth and has a big control programme.
- The Vaal River near Orkney had a 6km backup of water hyacinth behind chains
Even the smallest piece left behind will re-grow. And water hyacinth (Eichhornia crassipes - category 1) - is such a worldwide problem that a Global Working Group comprising over 30 scientists from 11 countries meets every two years to discuss control options for this single species. The danger is that an excess of these plants alters the pH of water, kills fish by blocking out sunlight, produce an excess of minerals, which in turn causes an increase of algae.
Vital statistics on invasive aliens
Only 15% of tree species introduced to South Africa are regarded as invasive. 750 tree species and 8 000 herbaceous species introduced into South Africa 1 000 introduced species are naturalised, 200 are invasive.
- 84 species introduced from South and Central America
- 14 from North America
- 30 from Australia
- 29 from Europe
- 36 from Asia
- 45% of species from Australia have become important pests
Did you know? IAPs have been around for a long time
Since 1652, when Dutch horticulturist Hendrick Boom set up a garden for the Dutch East India Company in Cape Town, exotics ranging from English oaks to Australian acacias have been arriving on our shores. For example, the timber industry introduced blue gums (Eucalyptus globulus) and black wattle (Acacia mearnsii) to KwaZulu-Natal in 1839 and by 1904 there were 75 000 hectares of wattle plantation in and around Durban.
THE WORST AQUATIC INVADERS
Remove and destroy. Water hyacinth must be destroyed by law, as the costs to taxpayers of controlling it when it takes over a dam out weigh any pleasure one may derive from having this plant in your water feature. Pic: Kay Montgomery
Remove and destroy. Water lettuce (Pistia stratiotes) is a highly ornamental invasive alien aquatic that should never be allowed to flourish in private ponds in the Eastern Cape. Pic: Lukas Otto
Remove and destroy. Parrot’s feather (Myriophyllum aquaticum), a South American floating aquatic plant with pale green, finely divided, feather-like leaves is a Category 1 invasive alien aquatic weed. Pic: Lukas Otto
