Helianthus pauciflorus Nutt.
CC = Amb
CW = 5
MOC = 33
Family - Asteraceae/Heliantheae
Habit - Perennial forb with relatively long-creeping, thick, branched rhizomes, often colonial.
Stem - Solitary, erect, to 1.5 m, roughened with short, stiff, pustular-based hairs.
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.
Heads - Radiate. 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, surfaces mostly glabrous.
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.
Flowering - August - October.
Habitat - Upland prairies, glades, openings in upland forests.
Origin - Native to the U.S.
Lookalikes - Broadly, numerous species of Helianthus, especially H. hirsutus, H. divaricatus, and H. occidentalis.
Other info. - This species is found in scattered locations around the state, but is uncommon in the Ozark and Mississippi Lowlands Divisions. It occurs in the eastern half of the continental U.S., less commonly in Atlantic Coast states. 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.
Photographs taken at Victoria Glade Conservation Area, Jefferson County, MO, 8/27/2010 and 8-25-2015 (SRTurner).