QUESTION: MY KIKUYU LAWN HAS BEEN OVERRUN BY CREEPING SORREL THAT PRODUCES A SMALL YELLOW FLOWER. I STARTED MOWING THE LAWN HIGHER AND HAVE BEEN USING TURFWEEDER AND EVEN REPLACED SOME OF THE BADLY AFFECTED AREAS WITH NEW LAWN. JUST WHEN I THOUGHT I HAD WON, THE PROBLEM NOW HAS BECOME WORSE. BEFORE APPLYING THE TURFWEEDER I WOULD FERTILISE AND WATER WELL AND EVER RESORTED TO SPRAYING THE LAWNMOWER AFTER USE. PLEASE ADVISE.

The extermination of a well established population of creeping sorrel aka Oxalis corniculata is almost impossible except by very careful and diligent effort. If the existing soil layer is full of Oxalis seeds and plants, it can be replaced with or covered by a sterile top-dressing or mulch. Poisons can be used, but have undesirable side-effects as they kill the good with the bad; and weeds can also become immune to them unless the treatment is done with different chemicals. Continue using Turfweeder if you wish but try alternating this with Banweed and Hormoban from Efekto.

Deep shade alone seems to conquer this plant, but then it is not known how long the seed will be viable in the soil so I would not recommend covering the affected areas.

The plant spreads by means of rhizomes (underground stems) and in also produces an abundance of small, triangular seeds. To remove it manually you will need to locate the base of the plant, a small bulblet, and dig up the entire plant, including the shoots, stems and leaves. Any remaining bits have the potential to sprout new plants.