Common yellow woodsorrel
Native to eastern US; introduced to parts of most of the western states; most common in Arizona and New Mexico
Woodland, canyons, meadows
Alternate, divided into 3 obcordate leaflets, between 0.2 and 0.8 inches long
Stems of oxalis stricta are largely unbranched, growing vertically upwards to heights of around 2 feet, and have a covering of short, bristly hairs, variable in length. Hairs point outwards. Leaves are borne along the stems; they are divided into three pale green, heart-shaped leaflets, with appressed hairs on the surfaces and protruding hairs along the margins. Leaflets are non-overlapping. They fold up along the midvein at night, reopening the next morning.
The inflorescence is an open, terminal cluster, generally containing between two and five heads, each borne on hairy stalks up to 4 inches long. Flowers have five yellow, clawed petals, fused at the base, and a center of ten yellow stamens arranged around a compound pistil. Underneath are five, green, pointed sepals, their tips often visible from above, between the petals. The base of the flower cluster is subtended by a pair of small bracts.