Khaki weed is a low-growing perennial plant with creeping stems that can at first glance appear to be a relatively benign ground cover.
Don’t be fooled. As they mature, those clusters of green or pale yellow flowers will develop into sharp burrs that hurt and are easily spread by animals, clothing and even car tyres.
What is Khaki Weed?
Thought to have come from Central and South America, Khaki Weed is found across all mainland states.
Also known as Khaki Burr, it’s particularly common in New South Wales and Queensland and grows in all but the driest environments.
Khaki Weed thrives in disturbed soil, quickly forming a dense mat of vegetation in lawns, orchards, along roadsides and on nature strips, and is known to invade grasslands and conservation areas.
It is regarded as an environmental weed in large parts of northern Australia.
Khaki Weed is distinguishable from harmless ground covers by the hairy reddish stems up to 60cm long that can produce roots at the nodes.
The oval shaped leaves grow in pairs, with one bigger than the other, on short stalks.
Khaki Weed produces small clusters of flowers in the leaf forks from spring to autumn, which develop sharp points at the tip and prickles at the base as they mature.
The seeds are hidden inside a burr that readily attaches itself to animals, socks, trousers and vehicles, as well as being spread by moving water or in lawn clippings.
Fragments of stem can also take root and generate new plants.
Khaki Weed has a thick tap root and during dry conditions the plant can die back, reshooting in spring or summer after rain.
How to Kill Khaki Weed in Your Lawn
Getting Rid of Khaki Weed Naturally
Because of its rapid growth and habit of putting down roots at nodes as well as spreading by seed, it’s important to take care with removing Khaki Weed.
The best way to get rid of Khaki Weed is to dig it out when the plant is small, before it flowers and develops those nasty, prickly burrs.
Take care not to drop any pieces of stem or leaf and make sure you’ve got the entire root to prevent reshooting.
Always put Khaki Weed in the bin or burn it to avoid escapes. Never put pieces in green waste or compost.
There are several organic methods of killing Khaki Weed, such as hitting it with boiling water or vinegar.
In both cases, be careful not to spill the liquid on your lawn or other plants because it will kill anything it touches, and always wear gloves to reduce the risk of skin irritation or burning yourself.
Boiling water: Pour the boiling water into the centre of a small plant for best results, which should be visible within a day or two. It might take a few repeat applications for the damage to extend to the root.
Vinegar: Add one cup (250ml) of salt – table salt is fine – to one litre of vinegar and 1 tablespoon of dishwashing liquid. Stir to dissolve and then carefully paint the mixture onto the weeds.
It will burn broadleaf weeds on a warm, sunny day, but repeat applications may be necessary as new seedlings emerge until the root is dead.
Using a Herbicide to Kill Khaki Weed
There are several herbicides suitable for controlling Khaki Weed. Some contain a single active ingredient while others have a combination of two or three.
Always wear the appropriate protective equipment – gloves, safety glasses etc – and read the product label before using any herbicide.
Also check whether the product is suitable for use on your grass type.
Some labels will recommend adding a surfactant, also known as a wetting agent, to the mixed weed killer to improve spray coverage and boost its effectiveness.
How Long do Herbicides Take To Work?
Signs of yellowing or wilting can appear in as little as one to 24 hours, but it takes time for the plant to absorb the poison and translocate it down to the fleshy root for a complete kill.
It can take up to three weeks for plants to die off and repeat applications may be necessary for controlling advanced weeds.
Some products can cause slight browning of grass if used in hot conditions.
When to Apply Herbicides?
Weather should be cool, dry and still, with temperatures under 30oC before and after application, and no rain expected within 24 hours.
Your lawn should be well-watered, experiencing no moisture stress, and the soil damp.
For best results do not mow or fertilise your lawn for seven days before or after application.
Killing Khaki Weed Without Damaging Your Lawn
It’s not easy, but it is possible to kill Khaki Weed without damaging your lawn.
As is the case with all weeds, prevention is better than playing catch up.
A thick, healthy, vigorously growing lawn that is well-fed and watered and mowed at the right height and frequency will not only withstand infiltration by most of the common weeds, it will recover faster from any weed control method should the occasional weed take root.
Organic methods such as boiling water or a vinegar mix should only be applied directly to individual weeds. Don’t use them too often or over a large area because they can also change the pH of your soil and kill off the beneficial microbes that help keep your lawn in top shape.
Shade
Maint.
Drought
Wear
$12–$18/m² 
