Most willow herbs are not large flowers and are often overlooked or mistaken for flowers in the pink family. Pinks, however, have 5 petals instead of the 4 that are found in willowherbs. This species is found throughout the United States except for the Deep South. It spread to Europe in the early 20th Century. The fringed willowherb is a member of the Onagraceae family that contains the evening primrose, fireweed as well as many species of willowherbs.

This species is a hairy perennial plant that has thin stems up to 4 feet high. The opposite leaves are lance-shaped and thickly veined. The leaves and stem are covered in bristly hairs and glands. At the end of the stems are clusters of pink, light purple or white flowers. These have four petals that are deeply notched to form two lobes. The petals have darker veining. The stigma is club-shaped. The petals merge to form a long flower tube. The fruit is a hairy capsule up to 10 centimeters long. The seeds are downy and can travel long distances in the wind.

This species is a wetland plant but can also be found in a great variety of habitats, including disturbed areas or along roadsides. It is also called the American willowherb, slender willowherb, or Northern willowherb. There are three recognized subspecies of the fringed willowherb.