Helianthus microcephalus |
Helianthus annuus |
|
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small woodland sunflower, small-head sunflower, woodland sunflower |
common sunflower, hairy leaf sunflower, sunflower |
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Habit | Perennials, 20–200 cm (with crown buds). | Annuals, 100–300 cm. |
Stems | erect, glabrous. |
erect, usually hispid. |
Leaves | cauline; opposite or alternate; petioles 0.3–3 cm; blades (greenish, at least abaxially, 3-nerved at bases) lanceolate, 7.2–15.5 × 1.3–4 cm, bases cuneate, margins entire or serrate, abaxial faces tomentulose, densely gland-dotted. |
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. |
Peduncles | 1–3(–8) cm. |
2–20 cm. |
Involucres | cylindric, 5–7 mm diam. |
hemispheric or broader, 15–40(–200+) mm diam. |
Ray florets | 5–8; laminae 10–14 mm. |
(13–)17–30(–100+); laminae 25–50 mm. |
Disc florets | 15–22; corollas 4–5.5 mm, lobes yellow; anthers dark, appendages dark. |
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). |
Phyllaries | 12–17, lance-linear, 3–6.5 × 1.5–2.5 mm, (margins ciliate) apices acuminate, abaxial faces glabrate, not gland-dotted. |
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. |
Heads | (1–)3–15+. |
1–9. |
Cypselae | 3.5–4.2 mm, glabrous; pappi of 2 aristate scales 1.5–2.2 mm. |
(3–)4–5(–15) mm, glabrate; pappi of 2 lanceolate scales 2–3.5 mm plus 0–4 obtuse scales 0.5–1 mm. |
Paleae | 5–7 mm, 3-toothed (apices hairy). |
9–11 mm, 3-toothed (middle teeth long-acuminate, glabrous or hispid). |
2n | = 34. |
= 34. |
Helianthus microcephalus |
Helianthus annuus |
|
Phenology | Flowering late summer–fall. | Flowering summer–fall. |
Habitat | Open woodlands, shaded roadsides | Open areas |
Elevation | 10–900 m (0–3000 ft) | 0–3000 m (0–9800 ft) |
Distribution |
AL; AR; CT; DC; FL; GA; IA; IL; IN; KY; LA; MD; MI; MN; MS; NC; NJ; OH; PA; SC; TN; VA; WV
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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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Discussion | Helianthus microcephalus is distinguished by its relatively small heads, which have relatively few phyllaries, ray florets, and disc florets, as well as the usually tomentulose abaxial faces of the leaves. Hybrids with H. divaricatus are known. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 21, p. 163. | FNA vol. 21, p. 149. |
Parent taxa | Asteraceae > tribe Heliantheae > subtribe Helianthinae > Helianthus | Asteraceae > tribe Heliantheae > subtribe Helianthinae > Helianthus |
Sibling taxa | ||
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 | |
Name authority | Torrey & A. Gray: Fl. N. Amer. 2: 329. (1842) | Linnaeus: Sp. Pl. 2: 904. (1753) |
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