Oxalis (Oxalis corniculata L.) is a perennial herb that is considered a troublesome weed in many lawns and gardens. This broadleaf weed, also known as creeping woodsorrell, has clover-like leaves with yellow, purple or green flowers when in bloom. Oxalis spreads throughout the landscape by spreading at the stems from the roots and through the vast production of seed. Although oxalis can be difficult to kill, methods are available to keep this weed under control.
Apply pre-emergence herbicide to lawn in early spring with a broadcast spreader. You can use a handheld spreader for gardens or small areas of grassy turf. You can purchase pre-emergence herbicides at home improvement and hardware stores or local nurseries. Some pre-emergence herbicides used to suppress the growth of oxalis are pendimethalin, prodiamine and dithiopyr. Read the label of any herbicide thoroughly to be certain it suppresses the growth of oxalis, a broadleaf weed, and not other desired plants in the lawn or garden.
Pull out any emerging oxalis by hand. Some oxalis may grow in the lawn or garden despite pre-emergence herbicide treatment. The best way to prevent spreading is to pull each weed out entirely with the root.
Apply post-emergence herbicides as necessary during the growing season. Post-emergence herbicides, like those that contain the chemical triclopyr, are made to kill existing oxalis weeds. You can also purchase these herbicides at a local home improvement center or nursery, and they come in concentrated strengths or premixed in spray bottles. If using concentrated herbicide, mix with water in a garden sprayer according to the manufacturer's directions. Read the herbicide label carefully before applying to avoid killing desired plant life.