Flowers - Corolla tube 1.2mm long, glabrous, white, 5-lobed. Lobes blunt, rounded, -1mm long, 1mm broad, glabrous, with conspicuous fornices at corolla throat. Fornices white. Stamens 5, included, adnate at base of corolla tube, alternating with corolla lobes. Filaments .1mm long, white, glabrous. Anthers yellowish at first, reddish with age, .3mm long. Ovary 4-lobed, green, tuberculate, .8mm broad. Style short, included, .2mm long, glabrous, pale yellow to whitish. Stigma capitate. Calyx tube to .3mm long, pubescent, 5-lobed. Lobes ovate, 1.2mm long, acute, antrorse pubescent externally, glabrous internally, erect in flower, spreading in fruit. Calyx accrescent. Fruit a 4-parted globose capsule, 5-6mm in diameter, with dense bristles. Bristles glochidiate.
Leaves - Alternate, petiolate. Petiole winged. Blade to +/-20cm long, +/-7cm broad, ovate to elliptic-ovate below, becoming lance-oblong above, scabrous, acute, entire, reduced above.
Inflorescence - At anthesis flowers in a compact coiled cymes at tip of stems. Inflorescence quickly elongating and become racemose, to +20cm long. Fruits pendant, subtended by small bract. Petioles to 2mm in flower, elongating in fruit to +4mm long, dense pubescent.
Flowering - June - September.
Habitat - Open woods, thickets, waste ground.
Origin - Native to U.S.
Other info. - The fruits cling to clothing and hair better than probably any other species. Viewed under a microscope, the bristles of the fruit have a ring of retrorse barbs at their apices (glochidiate).