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The single mostly costly conservation intervention is the control of invaders. Here in the Crocodile River Reserve, the scourge of invaders threatens the entire grassland and the wetlands. Even the higher, less accessible areas of bushveld are under threat.

What is the threat?

Invaders replace the natural plants, changing not only the rich variety of naturally occurring wildflowers, grasses and trees, but also the animals. Many other species rely on the plants for food and shelter. As the type of animal attracted to, or able to live off the natural vegetation changes, so does the selection of all other creatures. The ripple effect alters the entire “system”.


What is the threat to humans?

A host of things. A change in water quality and quantity is a significant threat. Invaders thrive at the expense of other plants which are adapted to this climate. The invaders take more water and give fewer – if any – services back in return. Natural vegetation works to store carbon, to recycle air, to purify water, to prevent soil erosion, and other services generally called ecosystem services. Invaders cannot offer the same services as the presence of these plants usually results in an imbalance of sorts within the system. Suddenly a smooth running ecosystem service or nature’s own infrastructure, is lopsided, and fails to deliver at optimum levels. The whole system deteriorates and degrades. Water is no longer available in the same quantity, or at the same quality; soil washes away; carbon is released into the atmosphere; and the whole system is less attractive.

"It is evolution. Things change." 

Evolution would allow for natural enemies to grow stronger too. Enemies (or prey) keep the system in check, ensuring no one thing dominates. A typical local invader – the pompom weed – takes over, dominates, and consequently wipes out the food available for grazing and foraging. It has no natural enemy here as the enemies were not introduced into the country alongside the invader, nor has there been time for an enemy to evolve. The artificial introduction (or accidental release) of an organism is not an evolution. We humans carried plants across continents, not the wind.    

It goes: “I couldn’t resist. It was so beautiful I just had to pop a [seed/slip/cutting/plant] into my luggage. Isn’t it lovely? Planted it right there in the garden. Want a piece? It grows so quickly!”

Top 10 Local Invaders

  1. Pompom
  2. Verbena, a “cousin” to the pompom
  3. Lantana, in shades of orange or pink. Toxic.
  4. Syringa, fast growing tree
  5. Giant reed, choking our wetlands
  6. Mexican poppy, estabishes quickly in disturbed areas and roadsides
  7. Queen of the Night, grows easily from fallen cutting
  8. Bugweed, fast growing, unattractive tree
  9. Yellow Bells, a spring-flowering tree
  10. Red Sesbania, a small tree
  11. Tickseed, a cheerful and attractive bright yellow flower
  12. Fountain Grass, an attractive grass with slightly purple flowers

See images below. 

Other threats

  1. Poplar, choking up our riverine and wetland area
  2. Wattle, a commercially grown tree, seeds are the real problem
  3. Bankrotbos, a death-knell to grazing
  4. Tipunana tree, fast growing tree, very tall

 Lurking in the garden...

  1. Various privets (Category  3),
  2. Sword ferns (Category 3),
  3. Wandering jew (Category 1b),
  4. Periwinkle (Category 1b),
  5. Bauhnia – the Butterfly orchid tree (Category 3),
  6. Bottle brush (Category 3),
  7. Mulberry tree (Category 3),
  8. Spanish broom (Category 3),
  9. English/Madeira ivy (Category 3),
  10. Jacaranda tree (ONLY allowed within 50 meters of the main house, and only well-estbalished trees)

The statements which will cause the battle to be lost

“I can’t do anything until my neighbour does”

While everyone plays a waiting game, the infestation gets worse, and the one that will be impacted is YOU. See “I don’t have the money”.

“I don’t have the money/time to do anything”

Left unattended, the invasion will increase EXPONENTIALLY. One plant will be 5 next year; 5 plants will be 25 the year thereafter; 25 will be waves of growth in different stages of maturity and will now be a carpet of growth.   The more the plants, the higher the cost to treat, the more time it will take to bring to manageable levels.

“Why should I do something when the roads / Pelindaba / [insert any other organisation/place] is such a mess?”

Those are “out there”; in HERE we can do something. And more: be an active citizen. Complain, lobby, badger and insist that those others are compliant with the law so that your efforts last.

“I don’t know what to do”

See hints, tips and techniques.

“I cut the flowers every year but nothing works”

It is a myth. Cutting the flowers only has the result of increasing the number of flowers a single plant will produce – typically, five other blooms will form in the place of the one which was cut.

If you are addressing the problem by cutting the flower, you have left the treatment too late. You will spend less time and money if you are start WELL before flowering. Go outside a take a photograph of the pompom infestation now. Stick the photo up on your fridge. That is your reminder for next season (when it WILL be worse). Start early.

You might cut off the flowers AFTER the treatment to prevent those flowers from producing seeds. You need to consider those blooms to be dangerous time bombs, and make them sterile. You may NOT transport cut flowers or dump them in your rubbish or compost. Why? Moving it makes your problem “mobile” and releases it on other people.

“What pompom?”

Walk about and check your property for invasive aliens. Know which plants are invasive (see Top 10 list, and 5 emerging threats) and take action. See it; recognise it; prevent the spread.

“I have hardly any [pompom] on my property”

To keep it that way, you need to manage the threat EVERY year. The plants will sneak up on you and become a field of invaders “overnight” if you are not active,
and vigilant.

Hints, tips and techniques

Manual removal is only practical if you have very few plants that are ISOLATED in occurrence. In other words, here a one plants and way over there another single plant.

Herbicides are effective – and dangerous. Use with great care and exactly according to instructions.

Never use herbicide near a water source (including a wetland and your borehole!)

Don’t keep your herbicide from one season to another and expect it to work. Buy what you need, and use it. If you can’t use it up, give it to someone who can.

Invest in a backpack sprayer. A hand held pump sprayer might be OK when there are very few plants, but will be exhausting to use and inefficient.   And if you have a large infestation, buy the best backpack sprayer you can afford; it will be worth it.

Do use a dye in the herbicide. It will help you to see where you have sprayed. Everyone will get confused when their eyes are on the ground looking for plants. One plant begins to look just like another in no time at all, and you will involuntarily crab-walk as you go from one alien to another.

Do use a “wetting agent” (a specially formulated oily substance). This helps to “stick” the herbicide to the plant leaves for a longer time – more herbicide is absorbed over the period and is able to get into the plant to kill it off.

Do not spray when temperature is higher than 280C. The plant takes measures to retain moisture, which effectively block the penetration of the herbicide. You are spraying to no purpose (and you will be hot and grumpy too).

The herbicide will need time on the plant. If it rains within 2 to 4 hours, you may need to re-apply.   Don’t spray in humid conditions, including misty days or early morning dew.

Keep the nozzle close to the ground, and spray the leaves. Cover the

flower with herbicide has no effect. It is the leaves which are the “powerhouse” of the plant and “disabling” the leaves will cause the whole plant to die.







mexican poppy

Mexican Poppy (in white or yellow)

prickly pear

Prickly Pear


Tickseed - looks like a Yellow cosmos