Helianthus petiolaris (Prairie Sunflower) - photos and description
General: Annual plant, single stems to branching growth habit. Entire plant rough-hairy to touch.
Flowers: Flower heads on long peduncles. Flower heads measured to 7.5 cm diameter, petals to 3 cm long, the central disc is dark brown, measured from 1 to 2 cm in diameter. Central disc is white-spotted. Bracts lanceolate to ovate, tapering gradually to a point, margins with short hairs, bracts measured 11 mm long by 5 mm wide.
Leaves: Leaves mostly alternate, a few leaves opposite, mostly wedge-shaped at their base, the leaf highlighted above blade measured at 8.5 cm long by 4.5 cm wide. Leaves entire.
Height: Height listed in Budd's Flora to 100 cm. We measured plants to 92 cm tall.
Habitat: Sandy areas and sand hills, also grows along roadways on light soils in south-western Saskatchewan.
Abundance: Common.
Origin: Native.
Synonym: Listed in some of the field guides we use as H. couplandii.
How to identify this species of Helianthus: To distinguish between this species and the other Saskatchewan annual, native sunflower, Helianthus annuus:
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 19th, sand hills in Douglas Provincial Park, about 175 km west of our home in Regina, SK.