Helianthus annuus |
Asteraceae (tribe Heliantheae) subtribe Helianthinae(synonym of Asteraceae tribe Heliantheae subtribe Helianthinae) |
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common sunflower, hairy leaf sunflower, sunflower |
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Habit | Annuals, 100–300 cm. | Annuals, perennials, subshrubs, or shrubs, (2–)20–500 cm. | ||||||||||||||||||||||||||||||||||||
Stems | erect, usually hispid. |
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Leaves | mostly cauline; mostly alternate; petioles 2–20 cm; blades lance-ovate to ovate, 10–40 × 5–40 cm, bases cuneate to subcordate or cordate, margins serrate, abaxial faces usually ± hispid, sometimes gland-dotted. |
usually mostly cauline, rarely mostly basal; mostly opposite (distal often alternate) or mostly alternate, rarely whorled; petiolate or sessile; blades (often 3- or 5-nerved) orbiculate or deltate to lanceolate or linear (and intermediate shapes), sometimes lobed, ultimate margins entire or toothed, faces usually hairy (often hispid to scabrellous), often gland-dotted. |
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Peduncles | 2–20 cm. |
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Involucres | hemispheric or broader, 15–40(–200+) mm diam. |
cylindric to hemispheric or rotate. |
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Receptacles | usually flat or convex, sometimes hemispheric or conic, usually paleate (epaleate in Lagascea; paleae usually falling, sometimes persistent, mostly oblong to linear, often conduplicate, herbaceous to scarious, apices sometimes ± 3-lobed or -toothed; becoming hardened perigynia completely investing cypselae in Sclerocarpus). |
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Ray florets | (13–)17–30(–100+); laminae 25–50 mm. |
0 or 5–30(–100+), neuter, or styliferous and sterile; corollas usually yellow to orange, sometimes partly or wholly brown to purple or red-brown to reddish. |
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Disc florets | 150+(–1000+); corollas 5–8 mm (throats ± bulbous at bases), lobes usually reddish, sometimes yellow; anthers brownish to black, appendages yellow or dark (style branches yellow). |
1 (Lagascea) or 10–200(–1000+), bisexual, fertile; corollas usually yellow to orange, sometimes brown to purple or reddish to red-brown, tubes shorter than or about equaling cylindric or funnelform throats, lobes 5, ± deltate (equal); anther thecae dark or pale; stigmatic papillae usually continuous. |
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Phyllaries | 20–30(–100+), ovate to lance-ovate, 13–25 × (3–)5–8 mm, (margins usually ciliate) apices abruptly narrowed, long-acuminate, abaxial faces usually hirsute to hispid, rarely glabrate or glabrous, usually gland-dotted. |
persistent, 4–45(–100+) in 1–6+ series (usually distinct, ± connate in Lagascea, broadly ovate to linear, subequal or unequal). |
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Calyculi | 0. |
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Heads | 1–9. |
usually radiate, sometimes discoid, borne singly or in corymbiform (paniculiform or racemiform) arrays (glomerules or second-order heads of 1–2-flowered heads in Lagascea). |
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Cypselae | (3–)4–5(–15) mm, glabrate; pappi of 2 lanceolate scales 2–3.5 mm plus 0–4 obtuse scales 0.5–1 mm. |
often ± compressed, flattened, biconvex, clavate, columnar, obovoid, obpyramidal, or prismatic (lengths usually 1–2 times diams.), glabrous or hairy (faces and/or angles); pappi 0, or (often readily falling or fragile, sometimes persistent) usually of (1–)2(–8+) (sometimes aristate) scales and/or awns, sometimes coroniform. |
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Paleae | 9–11 mm, 3-toothed (middle teeth long-acuminate, glabrous or hispid). |
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2n | = 34. |
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Helianthus annuus |
Asteraceae (tribe Heliantheae) subtribe Helianthinae |
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Phenology | Flowering summer–fall. | |||||||||||||||||||||||||||||||||||||
Habitat | Open areas | |||||||||||||||||||||||||||||||||||||
Elevation | 0–3000 m [0–9800 ft] | |||||||||||||||||||||||||||||||||||||
Distribution |
AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NS; NT; ON; PE; QC; SK; SPM; Mexico; intoduced nearly worldwide
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Mostly subtropical; tropical; and warm-temperate New World |
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Discussion | Helianthus annuus is widely distributed, including weedy, cultivated, and escaped plants. It is the only native North American species to become a major agronomic crop. Despite its considerable variability, attempts have failed to produce a widely adopted infraspecific system of classification. Forms with red-colored ray laminae, known from cultivation and occasionally seen escaped, trace their ancestry to a single original mutant plant. It hybridizes with many of the other annual species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Genera 17, species 363 (8 genera, 69 species, including 1 hybrid, in the flora). Circumscription of Helianthinae adopted here (i.e., that of H. Robinson 1981) is narrower than traditional circumscriptions (e.g., T. F. Stuessy 1977[1978]), which included genera here treated in Ecliptinae, Galinsoginae, and Rudbeckiinae. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 21, p. 149. | FNA vol. 21, p. 135. | ||||||||||||||||||||||||||||||||||||
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Synonyms | H. annuus subsp. jaegeri, H. annuus subsp. lenticularis, H. annuus var. lenticularis, H. annuus var. macrocarpus, H. annuus subsp. texanus, H. aridus, H. jaegeri, H. lenticularis, H. macrocarpus | subtribe Lagasceinae | ||||||||||||||||||||||||||||||||||||
Name authority | Linnaeus: Sp. Pl. 2: 904. (1753) | Cassini ex Dumortier: Fl. Belg., 71. (1827) | ||||||||||||||||||||||||||||||||||||
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