Yellow wood sorrel is an herbaceous annual or perennial with taproots when young, developing rhizomes with age. Flowers in unevenly branched panicles on long stems, with 5 yellow, rounded petals. Blooms May–October. Leaves alternate, trifoliate (like clover), the leaflets heart-shaped, light to dark green or copper to purple, often recurved, sometimes with grayish hairs. At the end of each day, the leaflets droop or fold downward, parallel to the stem; they spread again the next morning. Fruit an upright, pointed capsule to about 1 inch long.