Virginia Tech Weed Identification Guide

Tearthumb: Polygonum arifolium

Weed Description:  A branched annual with arrow-shaped leaves and stems with many prickles that are turned backward.   Tearthumb primarily occurs as an aquatic weeds of shorelines, marshes, and swamps.
Leaves:  Leaves are arrow-shaped, but with the basal lobes pointing outward (hastate).  Leaves are hairy, approximately 4 to 4 1/2 inches long, and occur on petioles that range from 1 1/4 to 4 1/2 inches in length.
Stems:  Branching, with many prickles turned oppositely (retrorsely barbed) from the direction of the stem.

Flowers: Occur in terminal spikes at the ends of branches with each spike containing 2 to 4 flowers.  Flowers are white to pink in color and occur on the ends of leafless flower stalks (peduncles).

Fruit:  A reddish brown, globular nutlet.

Identifying Characteristics:   The arrow-shaped leaves with bases that point outward and prickly stems help to distinguish tearthumb from most other aquatic shoreline weeds.  However, Arrow-leaved Tearthumb (Polygonum sagittatum) is very similar in appearance and growth habit but has much smaller, hairless leaves with lobes that encircle the stem unlike those of tearthumb.