Helianthus annuus (Common Annual Sunflower) - photos and description
General: Coarse plants with an upright, branching, leafy growth habit, large leaves, and thick stems.
Flowers: Flower heads to 11 cm diameter, central disk dark brown, cone shaped, measured to 4 cm diameter. Flower heads at top of stems and growing from leaf axils. Involucral bracts, abruptly attenuate, ovate, and having long hairs on the margin, measured to 2 cm long by 1 cm wide.
Leaves: Leaves ovate to deltoid, with a flat to cordate base, larger leaves are toothed. A large leaf measured at 19 cm long by 15.5 cm wide. Leaves and bracts are rough hairy with short hairs, stems with stiff, longer hairs. Lower leaves with long petioles, upper leaves have very short petioles. Leaves alternate.
Height: Height listed in Budd's Flora to 200 cm. We measured plants to 130 cm tall.
Habitat: Disturbed soil and roadsides on the Prairies. When you see sunflowers growing along highway shoulders in south central and south eastern Saskatchewan in August, it's more than likely this plant.
Abundance: Very common.
Origin: Native.
How to identify this species of Helianthus: To distinguish between this species and the other Saskatchewan annual, native sunflower, Helianthus petiolaris:
1) Flora of Alberta, H. petiolaris - "Leaves lanceolate to ovate, mostly cuneate at base, mostly entire, pubescence soft (we didn't see this), involucral bracts gradually attenuate, without long marginal hairs, disc 1-2 cm wide. H. annuus - Leaves commonly ovate, the lowest often cordate, mostly toothed, pubescence rough, involucral bracts abruptly attenuate, with conspicuous marginal hairs, disc 2-4 cm wide".
2) Taxonomic Reminder for identifying Saskatchewan Plants - distinguishes between the two by the shape of the involucral bracts, gradually attenuate for H. petiolaris, and abruptly attenuate for H. annuus.
3) "The Prairie Sunflower (H. petiolaris) can be distinguished from Common Annual Sunflower (H. annuus) by its heads displaying white-spotted disk centres, and the involucral bracts surrounding the heads not as long-tipped and only short-hairy on the margins." in Native Plant News, Vol. 2 No. 2, Saskatchewan's Flowers of the Sun: Helianthus spp." by Dr. Vernon Harms, June, 1997.
When and where photographed: The above photos were taken August 15th, edge of cultivated field, just outside the city limits of Regina, SK.