CREEPING WOODSORREL-Oxalis corniculata L.
- A spreading to prostrate perennial with weak creeping stems, 3 to 8 inches long, from a slender taproot. Reproducing by seeds, by stems rooting at the joints, and sometimes from slender underground rhizomes. The alternate leaves are divided into mostly 3 broadly heartshaped leaflets borne at the tip of the long leaf stalks, which have sharp tasting juice. The green, purplish, or bronze leaflets, closing and drooping at night, are hairless or thinly hairy.
- The flowers have 5 yellow petals, 1/8 to 1/3 inch long. They occur in clusters of 1 to 5 at the end of a slender flower stalk arising from the leaf axils. The yellowish seedpods are erect, but their short stalks are bent sharply downward. They are cylindrical, 5-angled, hairy, 1/3 to 1 inch long, and pointed at the tip. When the many seeds are mature, the seedpods open explosively, throwing the seeds some distance. The tiny reddish brown seeds are somewhat eggshaped but flattened, with 7 to 10 ridges on each face, and about 1/25 inch long.
- Creeping woodsorrel grows in dry or moist, usually shaded soil. Principally a nuisance in lawns and greenhouses, and often found close to buildings, this European introduction can be very aggressive and persistent when it becomes established in a lawn. Common in northern and southern Arizona; 100 to 8,000 feet elevation; flowering February to November.