Weed Spotlight - Creeping Oxalis

Author: Stefan Palm   Date Posted: 6 October 2021 

Creeping Oxalis (Oxalis Corniculta) is a broadleaf, highly invasive, hard to control weed. Most gardeners will have experienced this weed at one time or another and will know how persistent it is. So how can you control it?

Over the past month, we've had quite a number of people asking us for advice on how to control this weed in their lawn and garden. Ironically, most have had a good go at trying to get rid of it but have been unsuccessful for one reason or another.  Like many weeds, the secret to controlling it is a persistent, programmed approach, coupled with some knowledge about the weed. 

Creeping Oxalis commonly comes in 2 forms - green and purple. The green form is generally finer than the purple form however both can be said to have very small, clover-like leaves that are around 5mm or less in diameter. In Spring and Summer, the weed displays small yellow flowers which have 5 petals. When the flowers mature, they release a seed pod that is filled with fine seeds. Upon release, these seeds spread throughout your lawn and garden. 

  

Photo: Creeping Oxalis - Green form   

Photo: Creeping Oxalis - Purple Form

As the name suggests, creeping oxalis spreads quickly, both by seed and by its spreading nature. Its habit includes masses of fine runners that send down small taproots at regular intervals. This makes it impossible to pull out by hand leaving gardeners to eradicate it by chemical means. Even with the right chemical measures, you'll need to be patient in your approach with a good level of control often only achieved after months seasons of spraying. It is resilient, to say the least, and can easily re-invade through seeds germinating in the soil.

How do you control it? 

  • Use the right chemicals: When controlling creeping oxalis in lawns, I would advise you to use a selective turf herbicide containing MCPA and bromoxynil such as Yates Buffalo Pro Herbicide. This is the most versatile chemical as it is able to be sprayed on most of the common varieties of lawn including buffalo.  Avoid chemicals with Dicamba as this chemical can't be used on buffalo and is known to cause damage to nearby tree and shrub roots. I'd suggest adding some non-ionic wetting agent to your spray mix to enhance its effectiveness and I'd also resist the urge to mix up "extra-strong" batches of spray mix. Always mix up your chemicals as per the label - if you don't do this, you risk damaging your lawn.  
  • Spray at regular, timed intervals: You'll need to spray regularly (every 3-4 weeks) until you can no longer see evidence of the weed. This could mean 5-6 repeat sprays.
  • Avoid hose on applicators: With this weed, it's better to buy a concentrate chemical, mix it up in a sprayer and apply. Hose on applicators can tend to apply a solution that is too watered down resulting in less effectiveness against persistent weeds like creeping oxalis. They also don't allow you to add a wetter to the mix which is critical.  
  • Don't spot spray: Spray your whole lawn instead of spot spraying because it's hard to see the extent of how much weed you have. You only have to miss a small section of creeping oxalis to allow it to re-invade all over again. 
  • Be patient and persistent: Expect this weed to keep popping up so be prepared to keep attacking it. If you just hit it a few times and don't completely knock it out it will continue on its merry way - which usually ends up in total dominance of your lawn!

As I mentioned earlier, persistence is the key - expect it to bounce back and fight its demise every step of the way but be assured, you can win this battle!