Oxalis is a weed that can cause a real problem in the garden and the lawn as it is easily spread. It is often mistaken for clover, whose leaves are more rounded, whereas oxalis has green, heart-shaped leaves.
There are many forms of oxalis, but the common weedy ones are:
- Creeping oxalis (Oxalis corniculata) has tiny clover to heart-shaped leaves and yellow flowers. It is a common lawn weed with fine stems that creep under the runners of many lawn grasses. Seeds are spread via the lawnmower, soil and water. It also grows in garden beds and pots.
- Pink oxalis (Oxalis corymbosa) has dark brown, heart-shaped leaves produced by clumps of small brown bulbs. The weed easily spread via the many bulblets attached to the main bulb.
- Wood sorrel or soursob (Oxalis pes-caprae) has rounded clover-like leaves with tiny bright yellow flowers. It is prolific in winter but dies down as the weather warms.
The best form of control is to get on top of the weeds before they flower or spread more bulbs. When digging them out, remove the whole bulb and bulbs around it, which may include taking soil as well. Other options include covering the infested area with weed mat, cardboard or thick wads of newspaper. This removes light and stops the plant from photosynthesising, eventually causing death. Leave the covering in place for at least 12 months.
A well-mulched garden and dense, vigorous lawn can help keep oxalis at bay as there isn’t any room for them to grow. Feed gardens with a liquid fertiliser such as PowerFeed All Purpose including Natives, to encourage active plant growth and discourage weeds through competition and shading. Fertilising lawns with Seasol for Lush Green Lawns or Seasol for Buffalo Lawns during the growing season will keep the lawn dense and resistant to weeds.