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(updated January 21, 2021)

Annual Sunflower, Common Sunflower

Helianthus annuus L.

Asteraceae (Aster Family)

▲▼ young plants

▲▼ young plants

▲▼ young plants

 

▲ ▼ mature flowering plants

▲ ▼ mature flowering plants

▲ ▼ mature flowering plants

▲ ▼ mature flowering plants

▲ ▼ mature flowering plants

▲ ▼ mature flowering plants

 

▲▼ flowers

▲bracts at base of flower

▲rough hairs on stems

▲ common sunflower along highway in western Kansas

 

Helianthus annuus L., Annual Sunflower:  (Bayer Code:  HELAN; US Code HEAN3)

·         U.S. native summer annual that grows 3-10 feet tall with ridged, green stems that often branch at the nodes, particularly in full sun; both leaves and stems are rough-hairy

·         Leaves are opposite, heart-shaped to triangular, large, with 3 main veins emerging at base where petiole joins the leaf and toothed margins; petiole is long—often equal to, or slightly less than, length of leaf

·         Head inflorescences are 3-6 inches in diameter, the typical sunflower shape, but usually smaller than the cultivated species

·         Each head has 15-30 bright yellow disk florets (“petals”) that are have round-pointed tips, and are often kind of puckered where they join the head

·         There are from 100 to 1000 disk florets that are orange to brown

·         Bracts below the inflorescence are in several rows, large, oval-triangular or lanceolate, with an extended pointed tip; bracts are rough-hairy and stand out from the base of the head; edges of bracts have stiff hairs

·         Flowering from summer through autumn

·         Native annual sunflowers are usually have more branching and more, but smaller flowers than cultivated sunflowers

·         Allelopathic to itself (autotoxic) and other plants for several years after initial planting

·         Spreads rapidly by seed in cultivated fields, prairies, pastures, waste areas

·         Not often in strong competition with crops, but its allelopathic nature may make it undesirable in fallow field, where it can be a strong presence

·         A similar-appearing, more western relative, Prairie Sunflower (Helianthus petiolaris) has slightly smaller, more elongated-triangular to lanceolate leaves that are less hairy and somewhat glossy, with longer petioles, and much longer peduncles (stalks) below the inflorescences

 

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