Helianthus decapetalus
Helianthus porteri
hélianthe à dix rayons, thin-leaf sunflower
confederate daisy, Porter's sunflower
erect, glabrous.
erect, usually sparsely strigose, sometimes hispid as well.
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; opposite (proximal) or alternate;
petioles 0–0.2 cm;
blades (± 3-nerved distal to bases) narrowly lanceolate to linear, 5–11.5 × 0.15–1 cm, bases cuneate, margins entire (often ± ciliate proximally), faces sparsely strigose or scabrous to glabrate, sparsely gland-dotted.
2–12 cm (not gland-dotted).
1–10 cm.
hemispheric, 5–6 mm diam.
8–12;
laminae 20–25 mm.
7–8;
laminae (10–)15–20 mm.
40+;
corollas 6.5–7.2 mm, lobes yellow;
anthers usually dark brown to black (rarely reddish brown), appendages dark or reddish brown.
30+;
corollas 2.8–3.5 mm, lobes yellow;
anthers dark, appendages dark.
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.
11–17, linear, 5.5–8 × 0.8–1.3 mm (margins sparsely hispido-ciliate, hairs 0.5–1.2 mm), apices acute to acuminate, abaxial faces glabrate, not gland-dotted.
3–6(–10).
usually 5+.
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
2.2–2.3 mm, sparsely puberulent (bases and apices);
pappi 0.
-lucres hemispheric, 12–25 mm diam.
8–10 mm, 3-toothed.
(ovate) 3.5–4.6 mm, entire (1-toothed).
= 34, 68.
= 34.
Helianthus decapetalus
Helianthus porteri
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.)
Helianthus porteri was established at Rocky Face Mountain, North Carolina, following its introduction as part of an ecologic experiment. Where it occurs, H. porteri produces conspicuous massed floral displays when in bloom. It is remarkably similar morphologically in its reduced habit, epappose cypselae, conic receptacles, and unlobed, mucronate pales to Heliomeris (Viguiera sect. Heliomeris), and it is treated under Viguiera in most southeastern United States treatments; its style appendages and chromosome number agree with molecular phylogenetic data in placing it within Helianthus.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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