Helianthus laciniatus
Helianthus decapetalus
alkali sunflower
hélianthe à dix rayons, thin-leaf sunflower
erect, usually strigose or hispid to glabrate.
erect, glabrous.
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).
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.
4–13 cm.
2–12 cm (not gland-dotted).
hemispheric, 10–24 mm diam.
14–20;
laminae ca. 8–11 mm.
8–12;
laminae 20–25 mm.
40+;
corollas 4.8–5.8 mm, lobes reddish;
anthers purplish, appendages reddish (style branches yellow).
40+;
corollas 6.5–7.2 mm, lobes yellow;
anthers usually dark brown to black (rarely reddish brown), appendages dark or reddish brown.
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.
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.
1–9.
3–6(–10).
2.7–3.5 mm, glabrate;
pappi of 2(–3) aristate scales 1.4–2.5 mm.
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
7–7.8 mm, entire or 3-toothed (apices obtuse to acute, hispid-ciliate to glabrate).
8–10 mm, 3-toothed.
-lucres hemispheric, 12–25 mm diam.
= 34.
= 34, 68.
Helianthus laciniatus
Helianthus decapetalus
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.)
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.)
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