This native plant is a type of smartweed, but with a bit of a bite. The four-angled stems have numerous prickles that can cut into the skin if the plant is not handled carefully. The arrow-shaped leaves also have weak prickles on the underside leaf midrib. The species belongs to the buckwheat family.

The flower clusters are small and either pink or whitish. The plant can grow 2-6 feet high, but often seems to recline and intertwine with other vegetation. For that reason, it is also commonly called the arrow vine. Like all smartweeds, this plant has the typical sheaths where the leaves join the stem. These tend to be papery thin and brownish in color. There are no fringes on the sheath. The seed-like fruit is 3-sided.

The arrow-leaved tearthumb is found in wet places and marshes throughout eastern North America. The blooming period is from June to October.

The related halberd-leaved tearthumb (P. arifolia) has more prickles and wider leaves with flaring basal lobes. It has no prickles on the mid-vein. The Asiatic tearthumb (P. perfoliata) has triangular leaves, leafy sheaths that are often cup-shaped. The fruit is fleshy and blue.