Yellow woodsorrel is a broadleaf perennial, although it might act as an annual in some regions. Also known as oxalis, it has cloverlike leaves and yellow flowers, each with five petals. Plants spread by roots and seed.
This weed is difficult to control, and does best in thin turf watered frequently and lightly. Water thoroughly and fertilize properly. Dig out small plants or spot-treat isolated ones with a postemergence weed killer. Prevent new weeds with a preemergence herbicide with oxalis on the label.