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Published In: The Genera of North American Plants 2: 177. 1818. (14 Jul 1818) (Gen. N. Amer. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native

 

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11. Helianthus pauciflorus Nutt. (stiff sunflower, prairie sunflower)

H. rigidus Desf.

H. laetiflorus Pers. var. rigidus (Desf.) Fernald

Pl. 282 i, j; Map 1198

Plants perennial herbs, with relatively long-creeping, thick, branched rhizomes, often occurring as colonies of stems. Stems usually appearing solitary, 30–150(–200) cm long, sparsely to densely roughened-pubescent with short, loosely ascending to more or less spreading, short, stiff, pustular-based hairs. Leaves well developed along the stem (usually with 5–15 nodes), all or mostly opposite, sessile or with a poorly differentiated, winged petiole to about 1 cm long. Leaf blades 4–25 cm long, 2–6 cm wide, relatively thick-textured, lanceolate to elliptic-ovate or those of the uppermost leaves sometimes narrowly oblanceolate (mostly [2.0–]2.5–8.0 times as long as wide), flat, not folded longitudinally, tapered at the base, tapered gradually to a sharply pointed tip or angled more abruptly to a bluntly or sharply pointed tip, the margins finely toothed to nearly entire, flat, the surfaces strongly roughened with moderate to dense, minute, stout, pustular-based hairs, also with sparse to moderate, sessile, yellow glands, with 3 main veins, the lateral pair branching from the midnerve well above the base of the blade, arching upward. Inflorescences of solitary terminal heads or more commonly appearing as open clusters or open panicles. Involucre 12–20 mm long, 15–25 mm in diameter, shorter than the tips of the disc corollas, the bracts in 3 or 4 noticeably unequal, overlapping series, elliptic to oblong-ovate, narrowed to a bluntly or sharply pointed, tightly appressed tip, the margins with a fringe of short, spreading hairs, the outer surface glabrous or sparsely hairy but usually lacking glands. Receptacle convex, the chaffy bracts 8–10 mm long, narrowly oblong to narrowly oblong-oblanceolate, angled or short-tapered to a sharply pointed, green or purplish-tinged, minutely hairy tip, the outer surface also usually minutely hairy above the midpoint. Ray florets 10–21, the corolla 2.0–3.5 cm long, glabrous or the outer surface microscopically roughened. Disc florets with the corolla 6.0–7.5 mm long, the corollas reddish brown to dark purple (at least the lobes and the upper portion of the tube). Pappus of 2 scales 4–5 mm long, these lanceolate to narrowly triangular, tapered to a sharply pointed, often minutely awnlike tip, also usually with 2–8 additional minute, oblong scales 0.3–2.0 mm long. Fruits 5–6 mm long, narrowly wedge-shaped to narrowly obovate, flattened but more or less 4-angled in cross-section, the surface often with fine, ascending hairs when young but usually glabrous or nearly so at maturity, uniformly dark brown to black or sometimes with lighter brown streaks or mottling. 2n=102. August–October.

Scattered in the Glaciated and Unglaciated Plains Divisions, uncommon in the Ozarks and Mississippi Lowlands (Montana to New Mexico east to Maine and Georgia; Canada). Upland prairies, loess hill prairies, glades, and openings of dry upland forests; also pastures, railroads, and roadsides.

Specimens from 15 (so far) counties scattered nearly throughout the state are referable to Helianthus ×laetiflorus Pers., which comprises a series of hexaploid (2n=102) hybrids and backcrosses between H. pauciflorus and H. tuberosus. Steyermark (1963) and some other earlier authors considered this a true species, but its hybrid origins have now been confirmed with data from morphology, artificial crosses, and chemical compounds. It has a relatively broad distribution in the midwestern states (sometimes forming populations in the absence of both parents) and also occurs sporadically farther east. The natural range of the taxon is not known with certainty, as it has been cultivated as a garden ornamental for a long time and subsequently escaped from cultivation. Fertility apparently varies a great deal from plant to plant (Heiser et al., 1969). It differs most notably from H. pauciflorus in its yellow disc corollas and from H. tuberosus in its more strongly unequal, relatively short involucral bracts.

Helianthus pauciflorus was long known as H. rigidus, but the former is the older of the two available names (Spring and Schilling, 1990; Kartesz and Gandhi, 1990). Most botanists currently accept two morphologically overlapping subspecies within H. pauciflorus.

 

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1 1. Stems mostly 80–150(–200) cm long, with mostly 8–15 nodes below the inflorescence; uppermost leaves usually alternate; median and lower leaves mostly 8–25 cm long, oblong-lanceolate to narrowly ovate, tapered gradually to a sharply pointed tip ... 11A. SSP. PAUCIFLORUS

Helianthus pauciflorus Nutt. subsp. pauciflorus
2 1. Stems mostly 30–120 cm long, with mostly 5–10 nodes below the inflorescence; uppermost leaves usually opposite; median and lower leaves mostly 5–12 cm long, lanceolate to elliptic-ovate, angled to a bluntly or sharply pointed tip ... 11B. SSP. SUBRHOMBOIDEUS Helianthus pauciflorus subsp. subrhomboideus
 


 

 
 
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