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Published In: Species Plantarum 2: 904–905. 1753. (1 May 1753) (Sp. 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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2. Helianthus annuus L. (common sunflower)

H. annuus var. lenticularis (Douglas) Steyerm.

H. annuus var. macropocarpus (DC.) Cockerell

Pl. 281 g, h; Map 1189

Plants annual, with taproots. Stems solitary, (25–)50–300 cm long, stout, moderately pubescent with short, stiff, ascending, pustular-based hairs, these often breaking off toward the stem base, leaving the persistent expanded base. Leaves well developed along the stem (usually with 8–25 nodes), mostly alternate, long-petiolate. Blades of the stem leaves 7–40 cm long, 3–35 cm wide, ovate to triangular-ovate or broadly ovate-triangular (mostly 1.2–2.5 times as long as wide), flat or sometimes slightly drooping, not folded longitudinally, cordate to truncate, broadly rounded, or short-tapered at the base, tapered to a usually sharply pointed tip, the margins finely to coarsely and often somewhat irregularly toothed (rarely nearly entire), flat, the surfaces moderately to densely roughened, pubescent with minute, loosely appressed, pustular-based hairs, also with moderate to dense, sessile, yellow glands, more or less with 3 main veins, the lateral pair branching from the midnerve at the base of the blade. Inflorescences rarely of solitary terminal heads, more commonly appearing as open panicles. Involucre 10–30 mm long, (15–)20–50 mm in diameter (longer and much wider in cultivated forms), mostly shorter than or extending about to the tips of the disc corollas, the bracts in 3 or 4 subequal to somewhat unequal series, narrowly ovate to ovate, tapered to a sharply pointed, slender, loosely ascending to more commonly spreading or recurved tip, the margins with relatively long, stiff, spreading hairs, the outer surface moderately to densely pubescent with short (or occasionally longer), stiff, loosely ascending to spreading, pustular-based hairs, both surfaces also usually with small, sessile, yellow glands. Receptacle flat or slightly convex, the chaffy bracts 9–12 mm long (slightly longer in cultivated forms), narrowly oblong-triangular, usually 3-lobed above the midpoint, the lobes tapered to sharply pointed, straw-colored to dark purple, inconspicuously short-hairy tips, the outer surface usually glabrous below the tip. Ray florets 17–40 (more in cultivated forms), the corolla 2.5–5.0 cm long, variously glabrous or both surfaces inconspicuously hairy toward the base, or the outer surface minutely hairy and occasionally also with minute, sessile, yellow glands. Disc florets with the corolla 5–8 mm long, reddish brown to dark purple (at least the lobes and the upper portion of the tube; rarely yellow elsewhere). Pappus of 2 scales 2.0–3.5 mm long, these narrowly lanceolate-triangular, tapered to a sharply pointed, often minutely awnlike tip, papery, often also with 1–4 additional oblong scales 0.2–1.0 mm long. Fruits 3–7 mm long (longer in cultivated forms), narrowly wedge-shaped to obovate, flattened but usually more or less 4-angled in cross-section, the surface glabrous or more commonly densely and minutely hairy when young, but usually appearing glabrous or nearly so at maturity, uniformly black to variously with gray, brown, or white stripes or mottling. 2n=34. July–November.

Mostly absent from the Ozark and Mississippi Lowlands Divisions but scattered elsewhere in the state (nearly throughout the U.S.; Canada, Mexico). Upland prairies, openings of bottomland to mesic upland forests, and banks of streams and rivers; also crop fields, fallow fields, old fields, ditches, railroads, roadsides, and open, disturbed areas.

The common sunflower is the most important crop plant to have originated from a species native to the United States. It is the state flower of Kansas, where sunflower fields are a common sight. For a thorough account of this plant and its uses, see Heiser’s (1976) enjoyable book on the genus. Helianthus annuus is cultivated nearly worldwide for its edible seeds and for the oil produced from the seeds, which is one of the most important of the world’s vegetable oils for food production and also industrial and other uses. In recent years, the market for sunflower seeds for wild bird feeding also has become increasingly important in the United States. The species is cultivated as an ornamental, and plants also are used to a limited extent for fodder for livestock and for wildlife food plantings. At one time, Missouri was among the largest producers of commercial sunflowers in the country, but production has shifted primarily to other states, particularly North Dakota.

Heiser (1951, 1976) discussed the domestication of common sunflower. According to him, the species originally was native to the western states. However, the remains of fruits have been found by archaeologists in scattered prehistoric cliff shelters as far east as South Carolina (including sites in Missouri). Heiser noted that Native Americans had a long history of harvesting the plant from the wild for food, oil, and a yellow dye, which led to its establishment as a weed in and around sites of habitation and to its cultural dissemination among tribes during pre-Columbian times. The plant became cultivated at some point, which led to selection for traits such as fewer but larger heads and larger fruits. As early as the 1500s, the species was brought to Europe by early explorers and was cultivated there. It eventually became an important crop plant in Russia, where the “mammoth Russian” type, with its unbranched stem, greatly enlarged head, and large fruits, was bred. Cultivated forms of the common sunflower subsequently were reimported into the United States as a crop plant during the second half of the 1800s. Continued breeding both in Europe and in this country have resulted in a large number of commercially available cultivars adapted to different climates and for various uses. For example, Steyermark (1963) recorded a few collections from Holt County and the city of St. Louis of an ornamental dwarf form with the florets mostly converted to ray florets, which has been referred to under the name cv. ‘Nanus Florepleno.’ Interestingly, the large-headed sunflower that was independently domesticated by Native Americans survives in the American Southwest in a race known as the Hopi sunflower, which is cultivated on a very limited basis in modern times. The commercially important plants grown around the world today first originated as a result of efforts by plant breeders in Europe.

Although at times up to five taxonomic varieties of H. annuus have been recognized, a formal infraspecific classification mostly has been abandoned, owing to frequent hybridization that has blurred the boundaries between cultivated and wild plants (Heiser et al., 1969). The original, wild plants of the southwestern United States and adjacent Mexico at one time were called var. lenticularis and differ in their more numerous, smaller heads with narrower (4–7 mm) involucral bracts, smaller (2.0–3.5 cm in diameter) receptacles, fewer (17–26) ray florets with shorter (2.5–4.0 cm) corollas, and small (3–5 mm) fruits. Steyermark (1963) cited a single historical Missouri occurrence of this taxon from Jackson County (but see below). At the other extreme, the commonly cultivated plants (which rarely escape) were known in the past as var. macropocarpus and have an unbranched stem with usually a solitary terminal head having big (8.5–15.0 mm or more wide) involucral bracts, large (5.5–60.0 cm or more in diameter) receptacles, more numerous (30–70) ray florets with longer (3.5–10.0 cm) corollas, and large (6.5–15.0 mm) fruits. The sunflower that is widely distributed outside the original native range of the species has been called var. annuus and is more or less intermediate between the other two main variants for virtually every character. Heiser (1954, 1976) hypothesized that this weedy variety either arose through introgressive hybridization between the cultivated sunflower and the original wild type or that it evolved from the so-called camp-follower weed that became established around prehistoric habitations as an indirect result of harvesting of the species from the wild.

Given the complex biogeographical and ethnobotanical situation surrounding the species, it is not possible to address the issue of whether to consider the species native in Missouri with any confidence. The oldest Missouri herbarium specimen of common sunflower examined during the present study was collected in Cass County by G. C. Broadhead in 1876 and represents the var. lenticularis phase rather than the weedy phase. However, archaeological remains from digs at prehistoric dwellings indicate that a probably cultivated variant was present in Missouri hundreds or thousands of years ago (Heiser, 1978). Based on the herbarium record, the weedy variant moved into the state relatively early, reaching St. Louis County by 1896, Jasper County by 1905, and Marion County by 1914. It seems unlikely that H. annuus was ever a natural component of a native plant community prior to European settlement of the state, but the spread of the weedy variant into and across the state could be interpreted to have occurred without any direct human assistance.

Heiser (1947) studied natural and artificial hybridization between H. annuus and H. petiolaris. He noted that the hybrids have reduced fertility but are not totally sterile. Such hybrids have been reported from Cole and Jackson Counties and the city of St. Louis and can be very difficult to distinguish morphologically from one or the other parent.

 


 

 
 
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