Helianthus decapetalus
Helianthus laciniatus
hélianthe à dix rayons, thin-leaf sunflower
alkali sunflower
erect, glabrous.
erect, usually strigose or hispid to glabrate.
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; opposite or alternate;
sessile;
blades (green or grayish, 1- or 3-nerved) lanceolate, 5–9 × 0.5–3.5 cm, bases ± cuneate, margins entire or irregularly toothed to lobed, faces strigose to strumose, gland-dotted (adaxial sometimes glaucous).
2–12 cm (not gland-dotted).
4–13 cm.
hemispheric, 10–24 mm diam.
8–12;
laminae 20–25 mm.
14–20;
laminae ca. 8–11 mm.
40+;
corollas 6.5–7.2 mm, lobes yellow;
anthers usually dark brown to black (rarely reddish brown), appendages dark or reddish brown.
40+;
corollas 4.8–5.8 mm, lobes reddish;
anthers purplish, appendages reddish (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.
16–21, lanceolate, 6–7.5 × 1.8–2.5 mm (often subequal), (margins ciliate) apices acute, abaxial faces hispidulous or strigose to glabrate, gland-dotted.
3–6(–10).
1–9.
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
2.7–3.5 mm, glabrate;
pappi of 2(–3) aristate scales 1.4–2.5 mm.
-lucres hemispheric, 12–25 mm diam.
8–10 mm, 3-toothed.
7–7.8 mm, entire or 3-toothed (apices obtuse to acute, hispid-ciliate to glabrate).
= 34, 68.
= 34.
Helianthus decapetalus
Helianthus laciniatus
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 laciniatus reaches the northern extent of its range in New Mexico and Texas; it is relatively common in the Chihuahuan Desert areas of Mexico. It is similar to H. ciliaris; it usually has hairy stems as well as denser leaf indument that includes a greater number of subsessile, glandular hairs.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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