Oxalidaceae, the wood-sorrel family.
Plant: Low, upright or prostrate, to 12", with hairy stems, sour clover-like leaves, and yellow flowers. Annual.
Flowers: Yellow, with five petals, ten stamens, about 1/2" across. Sometimes with orange markings near the center.
Leaves: Basal or alternate, cloverlike, with three sessile, heart-shaped (obcordate) leaflets, about 1" overall. Smooth margins with a few silky hairs.
Fruit: An oblong capsule generally borne straight or at an obtuse angle to the stalk.
Habitat: Fields, disturbed areas, sometimes in part shade.
A European import, often a weed in gardens.
The leaves have a sour taste, and in small amounts can add interest to salads.
The sour quality is due to oxalic acid however, and it would be wise not
to eat the plant in quantity.
This genus is one of the plants known as shamrock in Europe.
A similar native species, O. stricta has fruit borne at a more acute
angle to the stalk.
Where to find it:
I have found this plant in a couple spots along the eastern border of the
park near the medical building parking lots.