This herbaceous perennial plant is about ¾–1½' tall and largely unbranched, except at the apex where the inflorescence occurs. The central stem is glabrous, 4-angled, and rather weak, causing the plant to lean over in the absence of supportive vegetation. The opposite leaves are up to 1½" long and 1/3" (8 mm.) across. They are lanceolate-linear or linear, smooth along the margins, sessile, and glabrous, except for a few hairs near the base of the lower leaves.
The central stem terminates in a dichotomously branching panicle of cymes. A pair of small green bracts occurs where the panicle branches. Each cyme is rather floppy and consists of 1-3 flowers on slender pedicels. Each flower is about 1/3" (8 mm.) across, consisting of a corolla with 5 deeply divided white petals (which can appear to be 10 petals), 10 stamens with brown or reddish brown anthers, a green pistil with 3 styles, and 5 green sepals that are lanceolate. Each sepal has 3 conspicuous veins along its outer surface, which is also somewhat ciliate or pubescent. The petals of the flower are longer than the sepals. The blooming period occurs from late spring to early summer and lasts about a month. An abundance of flowers is normally produced. Each flower is replaced by a straw-colored or light brown seed capsule that contains numerous small seeds. This capsule is ovoid-oblongoid in shape and open at the top, where a few erect teeth occur along the upper rim. Each seed is oval-orbicular and somewhat flattened; its surface is rough and pebbly. The root system consists of a shallow taproot and rhizomes. This plant spreads vegetatively or by reseeding itself, and often forms small colonies.