Stiff Sunflower (Helianthus rigidus) is a robust, upright perennial, typically reaching 50-150 cm in height. Its stems, covered in stiff, whitish hairs, are generally green with reddish tinges, becoming more pronounced in sunny locations. Stems are usually single, branching only within the flower cluster.
The plant's leaves are primarily basal, with stem leaves arranged oppositely on the lower and mid-stem, transitioning to sub-opposite or alternate near the top. Upper stem leaves are widely spaced. Leaf shape ranges from lance-ovate to oblong-lanceolate, featuring three prominent veins near the base. They taper to a point and to a wedge-shaped base, forming short, partially winged stalks (petioles), which are longest on lower leaves (less than 1/2 inch) and decrease in length upwards. Upper leaves may appear slightly folded along the midvein. Leaves are thick and rough, measuring up to 10+ inches long and 2-1/4 inches wide, with hairy undersides along veins and hairy margins. The leaf margins can be toothed or shallowly lobed (wavy). Upper stem leaves typically grow in an upward-pointing direction.
The Stiff Sunflower produces 1 to 10 flower heads at the top of the stem, each on a long stalk extending above the leaves; many plants have only one head. The hemispherical flower heads, 2 to 3 inches wide, are composite. They consist of 10 to 20 sterile, yellow ray florets (20-25 mm long, gland-dotted on the back) surrounding a central disc of 75+ fertile, bisexual tubular disc florets. These disc florets have reddish (occasionally yellow) lobes. The dark anthers of the five stamens tightly encircle the yellow, branched style. Upon opening, both stamens and style extend beyond the corolla, with the lobes curving backward. Disc florets open from the outer edge of the disc inwards. The flower head's base is composed of 25 to 35 overlapping, pointed, ovate phyllaries with finely hairy margins. The outer surface of the phyllaries ranges from smooth to hairy.
Distributions –
prairie; foothills; parkland
Light –
full-sun
Bloom Period –
mid-summer-to-fall
Height –
50 – 150 cm
20 – 60 in
Habitat –
Upland meadows, fields and roadsides.