How to Control Red Caustic Weed in Your Lawn

Red Caustic Weed is easily identifiable thanks to its reddish stems and small oval-shaped leaves of the same colour that are known to contain a sappy, white milk.

 Its aggressive growth habit allows it to outcompete healthy grass. This weed thrives in warm, humid environments and is commonly found along the eastern seaboard of Australia, particularly in Queensland, New South Wales, and northern Victoria.

Red Caustic Weed is most active in the warmer months, particularly from late Spring through early Autumn when temperatures and humidity are high.

It tends to invade Buffalo, Couch, Bermuda, Kikuyu, and Zoysia lawns, particularly those that are poorly maintained or experiencing thinning due to drought stress, poor soil health or thinning of the canopy due to excessive traffic. Red Caustic Weed can germinate in these bare patches, and its fast-spreading nature can soon have it outcompeting healthy lawn.

It spreads rapidly through both seed dispersal and underground rhizomes, making it difficult to control once established. The seeds can be transported by wind, water and even on garden tools, shoes, and pet fur, leading to widespread infestations if not managed promptly.

Red Caustic Weed can be managed effectively through horticultural practices like manual removal, chemical control through the use of herbicides or natural remedies, however the most effective remedy for tending to a Red Caustic Weed outbreak (and many weed outbreaks for that matter) remains immediate chemical control.

Manual Removal

Red Caustic Weed can simply be pulled out if the plant is still a juvenile and the outbreak isn’t too prolific. You’ll want to ensure you get the entire root system to minimise the chance of regrowth, so try removing after rainfall or after you’ve watered the lawn when the soil will be softest.

Using Herbicides

Chemical control is the most effective way to manage fast-spreading weeds like Red Caustic Weed. Currently, few herbicides are registered as being effective for Red Caustic Weed specifically, but many common active ingredients like Dicamba and MCPA have shown efficacy in its knockdown.

 LawnPride recommends Bow and Arrow as an effective way to treat Red Caustic Weed, which means comparable products like Contra M Duo and Estate would likely also be effective.

 The efficacy of liquid herbicides can be improved by using a surfactant like Wetter 600 to help the herbicide stick to the weeds, improving first round kill rate. It’s also recommended that you abide by the manufacturers recommendation when it comes to application rates, and ensure you’re spraying safely using their recommended protective equipment.

Natural Remedies

Natural remedies for Red Caustic Weed extend to ensuring the grass canopy is full and lush, minimising the chance of any outbreaks. This may mean adjusting your mowing height to help with the volume of the canopy. Some other natural remedies can include the use of vinegar or commercially available herbal solutions, but the efficacy of these products is questionable.

Luckily, invasive weeds like Red Caustic Weed can be managed through the use of a pre-emergent herbicide. Pre-emergent herbicides are a powerful tool that lawn lovers use to neutralise seeds before they even get a chance to germinate, which is a great way to keep foreign flora out of your established lawn.

As well as managing seasonal grasses like Poa Annua or wintergrass, a pre-emergent is also incredibly effective at managing undesirable weed outbreaks from plants like Red Caustic Weed and others, whose seeds are easily spread and can germinate quite quickly.

Pre-emergent herbicides will often provide up to six months cover. They’re typically applied in Autumn to protect lawns through Autumn and Winter, and then again in Spring to cover Spring and Summer.

They are available in liquid form through products like Spartan or Barricade, or can be purchased in granular form through products like Onset GR or Oxafert, the latter of which has the added benefit of a slow release fertiliser.

Mowing regularly at the correct height for your grass type can also help suppress weed growth by encouraging a dense, healthy turf that outcompetes invasive species.

Whether you’re looking at managing an outbreak that you’ve just identified using a broadleaf or selective herbicide, or you think preventing weeds through the use of a pre-emergent herbicide would be more effective, you can purchase common post-emergent herbicides like Bow and Arrow or Contra M Duo (not safe for Buffalo), and pre-emergent herbicides like Spartan, Barricade, Oxafert or Onset GR through the myhomeTURF online store.