Killing oxalis in a lawn requires an aggressive approach of pulling weeds as soon as they appear, using a pre-emergent herbicide and spraying any remaining plants with a weed killer. You must perform these actions consistently to keep the weeds from growing back.
- Remove the existing weeds
Pull the weeds from the lawn using a sharp spade or hoe. If the weeds are difficult to pull, use scissors to cut the plant at ground level. Cutting the foliage prevents the formation of seeds and robs the plants that spread underground of the energy they require to produce the expanding root system.
- Apply a pre-emergent herbicide
Choose a pre-emergent herbicide designed to prevent the growth of oxalis. Many general weed-and-feed products may be too weak to effectively control these types of weeds. Apply the herbicide per the manufacturer's directions when soil temperatures reach the ideal range.
- Spot treat oxalis with herbicide
If the oxalis survive the other treatments, use a herbicide to kill the plants. Fill a spray bottle with undiluted vinegar and a few drops of dish soap. Spray the vinegar at the base of the plant on a hot day to kill the weeds within 24 hours. If vinegar does not kill the oxalis, use a commercially prepared herbicide containing glyphosate instead.