Oxalis pes-caprae is a weed of gardens, orchards, cereal crops and native bushland. Sour sob is a long-lived herbaceous plant growing each year from underground bulbs. It produces a rosette of leaves at ground level and leafless upright flowering stems 15-30 cm tall. Its leaves are borne on stalks 10-22 cm long and have three heart-shaped leaflets. Its bright yellow flowers have five petals and are borne in loose clusters. These flowers open only during sunny periods and close again at night or during dull conditions.
Manual control
Constant and vigilant weeding prior to flowering. If you do not let the plant flower and continually weed you will eventually reduce the problem. However weeding is very difficult as the tiny bulblets drop off very easily and weeding can actually spread oxalis if you are not careful.
From SGLN’s 2017 weed guide.
Herbicides must be applied at the appropriate rate as specified on the label and all safety precautions followed. If chemical control is necessary near drainage lines or streams, use extreme caution as the effects on aquatic life can be devastating even in minute amounts. Always seek expert advice.
Chemical control notes from SGLN’s 2017 weed guide
Spot spray infestations with glyphosate (i.e. Roundup) just prior to flowering. Time of flowering will vary from year to year and between sites. As not all plants will be at the same stage further control will be required in the following years. Care must be taken to avoid off target damage when using herbicides in bushland. Always check the herbicide label before use.
These notes are from 2017, and some information, particularly herbicide information, may be out of date. Please ask local suppliers and do your own research in selecting herbicides if choosing chemical control.
