Common Sunflower

Helianthus annuus

Alternate names
Wild Sunflower

Weed Description
Common sunflower is an erect annual herb common throughout the United States and southern Canada. It is frequently a problem in agronomic crops, roadsides, and waste areas.

Leaves
Common sunflower leaves are arranged alternately along the stem except for new leaves at the base of the plant, which are arranged opposite. Leaves are simple, have serrated margins, and are triangular to heart-shaped in outline. Leaves are 4 top 12 inches in length and have hairs on both surfaces.

Stems
Stems are stiff and erect ranging from 3 to 12 m tall, often purplish with green specks, densly hairy, and branch towards the upper half of the plant.

Flowers
Seedheads contain bright showy yellow flowers reaching up to 3 inches in length. Disk florets are red to reddish brown.

Fruit
Seeds appear gray to black and measure 4 to 8 mm in length and as much as 2.6 mm in width. Common sunflower seeds are distinctly wedge shaped and flattened.

Roots
Fibrous root system from a taproot.

Identifying Characteristics
Common sunflower does not produce tubers as does Jerusalem artichoke. Additonal distinguishing characteristics include opposite leaves at the base with alternate leaf arrangement at the top and leaves that have hairs on both surfaces as well as the stem.

Office of Programs

University of Missouri

Common Sunflower

Helianthus annuus