Helianthus pauciflorus Nutt.

Stiff Sunflower

Helianthus_pauciflorus_plant.jpg
STATS

Native
CC = Amb
CW = 5
MOC = 33

© SRTurner

Family - Asteraceae/Heliantheae

Stem - Solitary, erect, to 1.5 m, roughened with short, stiff, pustular-based hairs.

Helianthus_pauciflorus_stem.jpg Stem.

© SRTurner

Leaf - Mostly opposite, sessile or with poorly differentiated petiole. Blades lanceolate, to 25 cm long, thick-textured, +/- flat, tapered at base, pointed at tip, with margins finely toothed to nearly entire. Surfaces strongly roughened with minute, stout, pustular-based hairs, also bearing sessile glands. Blades with 3 main veins, diverging well above base.

Helianthus_pauciflorus_leaf.jpg Leaf.

© SRTurner

Involucre - To 20 mm long, shorter than tips of disk corollas. Bracts in 3-4 unequal, overlapping series, tightly appressed, pointed at tip, margins with fringe of hairs, surfaes mostly glabrous.

Helianthus_pauciflorus_involucre.jpg Involucre.

© SRTurner

Helianthus_pauciflorus_head.jpg Flowering head.

© SRTurner

Florets - Ray florets 10-21, sterile, with corollas 2.0-3.5 cm long, yellow. Disk florets with corollas 6.0-7.5 mm long, reddish brown to deep purple. Pappus of 2 scales 4-5 mm long, sometimes also with 2-8 additional minute scales.

Helianthus_pauciflorus_florets.jpg Florets.

© SRTurner

Flowering - August - October.

Habitat - Upland prairies, glades, openings in upland forests.

Origin - Native to the U.S.

Other info. - This species is found in scattered locations around the state, but is uncommon in the Ozark and Mississippi Lowlands Divisions. It is fairly easily recognized by the combination of dark-centered flowering heads and narrow, opposite leaves. Two subspecies are recognized in Missouri: ssp. pauciflorus (more common) and ssp. subrhomboideus (relatively uncommon). These are differentiated by overall plant size, leaf arrangement at apex of plant, and leaf size and shape.
This species has been called Helianthus rigidus, but this name is apparently of more recent origin and thus disfavored. The name pauciflorus means "few-flowered," and indeed I have never seen more than a couple of heads per plant flowering at a time.

Photographs taken at Victoria Glade Conservation Area, Jefferson County, MO, 8-25-2015 (SRTurner).