Arrow-leaved Tearthumb

Polygonum sagittatum

Alternate names
Arrowvine, Arrowleaf knotweed, Arrowleaf smartweed

Weed Description
A branched annual with arrow-shaped leaves and stems with many prickles that are turned backward. Arrow-leaved tearthumb primarily occurs as an aquatic weeds of shorelines, marshes, and swamps.

Leaves
Without hairs, approximately 1 1/4 to 3 inches long, overall arrow-shaped in appearance. Leaf bases often encircle the stem and give the leaves even more of an arrowhead appearance.

Stems
Branching, with many prickles turned oppositely (retrorsely barbed) from the direction of the stem.

Flowers
Occur in small clusters at the ends of branches. Flowers are white to pink in color and occur on the ends of leafless flower stalks (peduncles).

Fruit
A brown to black nutlet.

Identifying Characteristics
The arrow-shaped leaves and prickly stems helps to distinguish arrow-leaved tearthumb from most other aquatic shoreline weeds. However, Tearthumb (Polygonum arifolium) is very similar in appearance and growth habit but has much larger hairy leaves with lobes that point outward unlike those of arrow-leaved tearthumb.

Office of Programs

University of Missouri

Arrow-leaved Tearthumb

Polygonum sagittatum