Yellow woodsorrel, also known as oxalis, is a summer annual, that can be perennial in some areas. Yellow woodsorrel grows on weak stems that branch at the base and may root at the nodes. The leaves form in groups of three leaflets on long petioles, and are alternate on the stems. Although sometimes mistaken for clover when not in flower, the leaves differ from clover in that they are distinctly heart shaped. The yellow woodsorrel flower is yellow with five petals and occurs in clusters. The seed pods range from ½- to 1-inch in length, have 5 ridges and are pointed. Yellow woodsorrel spreads by seeds which burst from the pods at maturity and may be scatted several feet. Yellow woodsorrel is found throughout the United States.
Since seeds may be projected several feet when seed pods mature, it is important to keep oxalis out of adjacent ornamental and flower beds as well as removing from turf areas. Dense, vigorous cool-season turf areas will resist infestation. Physical removal of single plants can be easily accomplished. Follow good turf management practices including disease and insect control and proper fertilization.
Properly timed pre-emergence herbicide applications can prevent oxalis germination. Spot treatments with a post-emergent broadleaf herbicide will clear out oxalis infestations. For optimum control, make your herbicide application when oxalis is actively growing and in the second trifoliate leaf to flower stage of growth.