Helianthus decapetalus
Helianthus praecox
hélianthe à dix rayons, thin-leaf sunflower
Texas sunflower
erect, glabrous.
erect to ± procumbent, hispid, hispid-hirsute, or hirsute.
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.
mostly cauline; mostly opposite;
petioles 5–9 cm;
blades deltate to ovate (sometimes constricted near middles, subsp. praecox), 3–9 × 2–7 cm, bases cordate, cuneate, or truncate, margins serrate to serrulate, abaxial faces hirsute to hispid, usually not gland-dotted.
2–12 cm (not gland-dotted).
15–40 cm.
hemispheric, 13–18 mm diam.
8–12;
laminae 20–25 mm.
11–16;
laminae 16–26 mm.
40+;
corollas 6.5–7.2 mm, lobes yellow;
anthers usually dark brown to black (rarely reddish brown), appendages dark or reddish brown.
35+;
corollas 5–6 mm, lobes reddish;
anthers dark, appendages purplish red (style branches reddish).
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.
30–39, lanceolate, 9–15 × 2–4 mm, apices short-attenuate to short-acuminate (subsp. praecox), abaxial faces hispidulous to hispid-hirsute.
3–6(–10).
1–3.
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
2.5–3.3 mm, ± villous;
pappi of 2 aristate scales 1.2–1.5 mm.
-lucres hemispheric, 12–25 mm diam.
8–10 mm, 3-toothed.
6.5–8 mm, 3-toothed (middle teeth acuminate, equaling or slightly surpassing discs, apices puberulent or bearded, hairs whitish).
= 34, 68.
Helianthus decapetalus
Helianthus praecox
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.)
Subspecies 3 (3 in the flora).
The taxa of Helianthus praecox were placed as subspecies of H. debilis by C. B. Heiser (1956). They were separated later, primarily on the basis of crossing results (Heiser et al. 1969). The subspecies appear to form a grade between H. debilis and H. petiolaris.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Stems procumbent to erect, branches horizontal, moderately hispid or hirsute; phyllary apices short-acuminate; paleae: middle teeth puberulent | subsp. praecox |
1. Stems erect, branches ascending, moderately or densely hirsute or hispid-hirsute; phyllary apices short-attenuate; paleae: middle teeth white-villous ("bearded"). | → 2 |
2. Stems moderately hirsute; leaves (at least larger) 3–7.5(–8) cm; peduncles 20–30(–35) cm; rays 11–13 | subsp. runyonii |
2. Stems densely hirsute or hispid-hirsute; leaves (larger) 8–9 cm; peduncles (25–)30–40 cm; rays usually 14–16 | subsp. hirtus |
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