Helianthus pauciflorus Nutt.

Stiff Sunflower

Helianthus pauciflorus plant

Family - Asteraceae

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

Helianthus_pauciflorus_stemStem.

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_leafLeaf.

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_involucreInvolucre.

Helianthus_pauciflorus_headFlowering head.

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_floretsFlorets.

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).



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