In Paul's Lawn Tips

This winter has seen a huge on-set of weeds such as soursobs presenting in many gardens and lawns. Many curious lawn owners have often complained about their appearance and want to know how to eradicate them without harming their plants.

Oxalis pes-caprae, or soursob as it is more commonly known, presents a dense mat of clover-like leaves along the surface, with stems of it’s signature yellow five petal flowers. It is extremely hard to kill, especially in lawns, as it has a fast-growing onion-shaped bulb system that can form as deep as 6cm below the surface.

Autumn is when oxalis is at its peak growing stage, as the plant’s rhizomes are continually producing multiple mini-bulbs. The rhizome is the white stem which connects the bulb to the clover plant. Cultivating is certainly not recommended during this time, as it will spread the rhizomes further, which in return causes more bulbs to form.

A successful way to kill oxalis is to spray the leaves before flowering begins with a systemic herbicide, such as roundup. However, this presents a problem when trying to rid them out of your lawn, as the glyphosate will most likely damage or kill your grass as well.

For your lawn, a successful point of attack is to purchase a selective broadleaf herbicide, such as Amgrow Sir Walter Buffalo Weed Control, which contains Bromoxynil, a nitrile herbicide, and MCPA (methyl chlorophenoxyacetic acid), a phenoxy herbicide. This product, produced specifically for Sir Walter lawns, attacks oxalis, as well as bindii, clover and dandelion but is still safe to use on other varieties of lawn, including couch and kikuyu. More than one application may be required for clover control. If so, ensure the treatments are spaced two weeks apart to let the herbicide soak in around the roots and bulbs of the weed.

Another method is to let the soursobs grow to flowering stage and then mow them off. This attacks the weed at its weakest stage and it is likely that you will kill most of the unwanted oxalis.

Remember:

  1. Never spray your lawn with a systemic herbicide containing glyphosate.
  2. Never cultivate the affected area.
  3. Ensure the broadleaf herbicide is specific to your variety of lawn.

If you have tried these solutions and are still having issues, please give us a call and we will be happy to guide you through your lawn issues and help you to achieve a weed-free lawn you’ll love.

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Showing 2 comments
  • David stevenson
    Reply

    G’day I would like to know if Metsulfuron Methyl “Ally” would be at all suited to killing Oxalis in Buffalo couch Kikuyu and ryegrass. It works wonders as a spot spray on my gravel driveway so I wonder if it is possible to dilute it enough to only target my weeds and not my turf.
    any advice is greatly appreciated
    cheers
    Dave

    • Turf Farm
      Reply

      Thank you for your question. The chemical you are referring to sounds like agricultural chemical that is not registered for turf. Please give us a call and we can discuss options of how to best eradicate Oxalis. If it is soursobs (Oxalis pes-caprae) you are wanting to eradicate we have found most herbicides don’t generally work on Soursobs as they are a bulb weed, not a seeded weed, so they will just keep coming back. Weed kill herbicides essentially just burn the top of the weeds, and don’t stop them from reproducing. You need to break the lifecycle and stop the plant from flowering. Continuous mowing is always the most efficient way every 7-10 days once they have grown above the lawn. With persistent over time the soursobs will reduce.

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