Helianthus decapetalus |
Helianthus gracilentus |
|
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hélianthe à dix rayons, thin-leaf sunflower |
slender sunflower |
|
Habit | Perennials, 60–200 cm (rhizomatous). | Perennials, 60–200 cm (taprooted). |
Stems | erect, glabrous. |
(reddish or purplish) erect, hairy. |
Leaves | cauline; opposite (proximal or all) or alternate (distal); petioles (1–)2–5 cm; blades (green, 3-nerved distal to bases) lanceolate to ovate, 7–21 × 4–10 cm, bases rounded to cuneate (often shortly decurrent onto petioles), margins usually serrate (moderately to notably in larger leaves), abaxial faces ± scabro-hispidulous, relatively sparsely gland-dotted. |
cauline; all or mostly opposite; petioles 0–3 cm; blades (1- or 3-nerved) lanceolate to lance-ovate, 5–11 × 2–3.5 cm, bases cuneate, margins entire or serrate, abaxial faces hispid, gland-dotted. |
Peduncles | 2–12 cm (not gland-dotted). |
2.5–30 cm. |
Involucres | hemispheric, 13–20 mm diam. |
|
Ray florets | 8–12; laminae 20–25 mm. |
13–21; laminae 15–25 mm (abaxial faces gland-dotted). |
Disc florets | 40+; corollas 6.5–7.2 mm, lobes yellow; anthers usually dark brown to black (rarely reddish brown), appendages dark or reddish brown. |
50+; corollas 5–6 mm, lobes reddish; anthers reddish brown, appendages yellow or dull orange (style branches yellow). |
Phyllaries | 20–25 (often reflexed), lance-linear to lanceolate, 11–16 × 2–3 mm (sometimes leaflike, longest surpassing discs by 1/2+ their lengths), (margins ciliate) apices attenuate, abaxial faces strigillose to glabrate, not gland-dotted. |
20–25, lanceolate, 4–8 × 1.5–3 mm, (margins ciliate) apices acute, abaxial faces hispidulous, gland-dotted. |
Heads | 3–6(–10). |
1–5. |
Cypselae | 3.5–5 mm; pappi of 2 aristate scales 3–4 mm. |
3–4 mm, glabrate; pappi of 2 aristate scales 2.5–3 mm. |
Invo | -lucres hemispheric, 12–25 mm diam. |
|
Paleae | 8–10 mm, 3-toothed. |
8–9 mm, subentire to weakly 3-toothed (apices acute, ciliate, gland-dotted). |
2n | = 34, 68. |
= 34. |
Helianthus decapetalus |
Helianthus gracilentus |
|
Phenology | Flowering summer–fall. | Flowering late spring–fall. |
Habitat | Mesic to wet woodland edges | Dry slopes |
Elevation | 10–1200 m (0–3900 ft) | 0–1800 m (0–5900 ft) |
Distribution |
AL; AR; CT; DC; DE; GA; IA; IL; IN; KY; LA; MA; MD; ME; MI; MO; MS; NC; NH; NJ; NY; OH; OK; PA; RI; SC; TN; VA; VT; WI; WV; NB; ON; QC
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CA; Mexico (Baja California)
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Discussion | Helianthus decapetalus is sometimes confused with Heliopsis helianthoides because of shared habitats and superficial similarities. The tetraploid cytotype of H. decapetalus intergrades (and apparently hybridizes) with H. strumosus, particularly in the southern Appalachians; individual specimens can be difficult to place in one or the other species. In addition to morphologic differences, H. decapetalus usually occurs in more mesic habitats, particularly along watercourses; H. strumosus is found in drier sites such as roadside slopes. Helianthus ×multiflorus Linnaeus is a sterile hybrid, often with “doubled” heads (in which disc florets are replaced by ray florets); it is cultivated and is sometimes included within H. decapetalus, e.g., H. decapetalus var. multiflorus (Linnaeus) A. Gray; its parents are H. decapetalus and H. annuus. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
|
Source | FNA vol. 21, p. 158. | FNA vol. 21, p. 168. |
Parent taxa | Asteraceae > tribe Heliantheae > subtribe Helianthinae > Helianthus | Asteraceae > tribe Heliantheae > subtribe Helianthinae > Helianthus |
Sibling taxa | ||
Synonyms | H. trachelifolius | |
Name authority | Linnaeus: Sp. Pl. 2: 905. (1753) | A. Gray: Proc. Amer. Acad. Arts 11: 77. (1876) |
Web links |