Weed Spotlight - Creeping Oxalis
Author: Stefan Palm Date Posted: 20 August 2018
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.
Creeping Oxalis most commonly comes in 2 forms - green and purple. The green form is generally finer that 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 which is filled with fine seeds. Upon release, these seeds spread throughout your lawn and garden.
Creeping Oxalis: Green form
Creeping Oxalis: Purple Form
As the name suggests, creeping oxalis spreads quickly, both by seed and by it's spreading nature. It's habit includes masses of fine runners that send down small tap roots at regular intervals. This makes it impossible to pull out by hand leaving gardeners to irradicate 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 several seasons of spraying.
When controling creeping oxalis in lawns, I would advise you to use a selective turf herbicide containing MCPA and bromoxynil such as Amgrow Bin-die. This is the most versitile 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.
You'll need to spray regularly (every 3-4 weeks) and I'd suggest adding some non-ionic wetting agent to your spray mix to to enhance it's effectiveness. Spray your whole lawn instead of patch spraying because its 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.
SoursobBy: Hennry Ringwood on 24 August 2018Is the creeping oxalis referred to commonly known as soursob or is this a different plant. The first picture looks like soursob to me but I am not sure about the flowers. Is it a relative and if so how do we tell the difference? PS I hate soursob!
Paul Munns Instant Lawn Response
Hey Hennry, That is a really smart question. Both Creeping oxalis and soursob are from the same genus - (Oxalis paniculata - creeping oxalis and Oxalis pes-caprae - Sour sob). This is why if you're looking at photos, the leaves can look similar. In actual fact, the creeping oxalis leaf is less than one quarter the size of a sour sob leaf. You'll also notice that the root zone is different too. Sour sobs have a tap root and a bulb whereas Creeping oxalis has a dense, fine and shallow root system. BTW, I hate Sour sobs too!