Yellow Woodsorrel (Oxalis stricta)
Yellow woodsorrel is a perennial (may act as warm-season annual) that reproduces by seeds and occasionally stem pieces. It emerges from a taproot and forms small, erect, bushy plants up to 20 inches tall. The stems are slender, gray-green, hairy, slightly ascending, and branched at the base. They will occasionally root at nodes. The leaves of yellow woodsorrel are alternate with three heart-shaped leaflets. They are pale green, up to 4/5 inch across with long petioles. Yellow woodsorrel flowers are yellow with five petals. They are up to 1/2 inch across and borne at end of stems in clusters of one to four. They are borne during May to September.
Yellow woodsorrel occurs in moist, open, fertile sites from mid spring to mid autumn. It seems to tolerate dry conditions when established.
To control yellow woodsorrel without chemicals, maintain turf density and health through proper culture. Mechanically remove or hand pull.
Apply preemergence herbicides before germination in spring; use postemergence herbicides in mid spring to early summer and/or mid to late autumn during active growth. This weed is difficult to control.