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.
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.
Source: Virginia Polytechnic Institute & State University