Helianthus decapetalus
Helianthus ciliaris
hélianthe à dix rayons, thin-leaf sunflower
blueweed, blueweed sunflower, Texas-blueweed, yerba parda
erect, glabrous.
decumbent to ± erect, glabrous or glabrate (glaucous).
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; mostly opposite;
sessile;
blades (often bluish green, 1- or 3-nerved) linear to lanceolate, 3–7.5 × 0.5–2.2 cm, bases ± cuneate, margins entire or serrate (usually ciliate and undulate), faces glabrous or glabrate to hispid.
2–12 cm (not gland-dotted).
(1–)3–13 cm.
hemispheric, 12–25 mm diam.
8–12;
laminae 20–25 mm.
10–18;
laminae 8–9 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 4–6 mm, lobes reddish;
anthers brownish red, appendages brownish red (style branches yellow).
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.
16–19, ovate to lance-ovate, 3–8 × 2–3.5 mm, (margins ciliate) apices obtuse to acute, abaxial faces glabrate to ± strigose, not gland-dotted.
3–6(–10).
1–5.
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
3–3.5 mm, glabrous;
pappi of 2 aristate scales 1.2–1.5 mm.
-lucres hemispheric, 12–25 mm diam.
8–10 mm, 3-toothed.
7–7.5 mm, subentire to 3-toothed (apices obtuse to acute, hairy, gland-dotted).
= 34, 68.
= 68, 102.
Helianthus decapetalus
Helianthus ciliaris
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 ciliaris is considered a noxious weed in some states. It can propagate vegetatively from detached pieces of rhizome and spread aggressively, especially in cultivated fields. It has been noted to occur in Idaho and Washington, where control measures have been taken to eliminate it.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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