Flower:

Loose branching clusters at the top of the plant, each branch with several whorls of 5 to 8 slender-stalked flowers, with separate male and female flowers on the same or separate plants. Flowers are less than 1/8 inch long, green to yellow to red, with 2 series of tepals (petals and similar sepals). The 3 inner tepals are egg-shaped with distinct venation across the surface (best seen when dry), with or without a minute, papery wing along the edge. The 3 outer tepals of male flowers are narrower than and about as long as the inner tepals, those of the female flowers are rather shorter. Tepals are widely spreading at flowering time, showing creamy yellow to red stamens or styles, and close up after pollination. Flower stalks are very slender and smooth.

Leaves and stems:

Leaves are mostly basal or on the lower stem, ¾ to 2½ inches long and up to ¾ inch wide, lance-elliptic, widest near or above the middle, blunt to pointed at the tip, with a pair of narrowly triangular, outward pointing lobes at the base (hastate), on a long stalk, becoming smaller and less lobed as they ascend the stem. Edges are toothless, surfaces are hairless.

At the base of the leaf stalk is a papery sheath (ocrea), brown at the base and whitish above, that surrounds the stem. Stems are erect to ascending, single or multiple from the base, unbranched except in the flower clusters, ribbed and hairless. Plants can form large colonies from creeping rhizomes.

Fruit:

A flower produces a single seed, wrapped in the persistent tepals that form a capsule-like structure.

Seeds are 3-sided, oval to egg-shaped with pointed tip, brown to dark brown, and about 1 mm long.

Notes:

Common Sheep Sorrel is a ubiquitous weed in much of North America, found primarily in open, disturbed soils of roadsides and degraded fields and prairies. It resembles the related Green Sorrel (Rumex acetosa), a larger plant with flowers and fruits about twice the size, the tepals with a broad wing around the edge, and much larger leaves with basal lobes that point downward (sagitate) rather than outward (hastate).