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hélianthe à dix rayons, thin-leaf sunflower

anomalous sunflower, western sunflower

Habit Perennials, 60–200 cm (rhizomatous). Annuals, 25–60 cm.
Stems

erect, glabrous.

erect, sparsely hispid.

Leaves

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 alternate;

petioles 1.2–5 cm;

blades ovate to lance-ovate, 4.5–13 × 1–4 cm, bases cuneate, margins entire, abaxial faces sparsely hispid, not gland-dotted.

Peduncles

2–12 cm (not gland-dotted).

4–9 cm.

Involucres

hemispheric, 20–27 mm diam.

Ray florets

8–12;

laminae 20–25 mm.

7–12;

laminae 18–37 mm.

Disc florets

40+;

corollas 6.5–7.2 mm, lobes yellow;

anthers usually dark brown to black (rarely reddish brown), appendages dark or reddish brown.

25+;

corollas 6.8–7.5 mm, lobes reddish;

anthers dark, appendages dark (style branches reddish).

Phyllaries

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.

11–23, laceolate to lance-linear or lance-ovate, 17–33 × 1–2.9 mm (notably surpassing discs), (margins ± ciliate) apices attenuate, abaxial faces usually sparsely hispid to hispidulous.

Heads

3–6(–10).

usually borne singly.

Cypselae

3.5–5 mm;

pappi of 2 aristate scales 3–4 mm.

4.6–9 mm, appressed hairy;

pappi of 2 linear scales 2–4.5 mm plus 4–6 scales 1–3.5 mm.

Invo

-lucres hemispheric, 12–25 mm diam.

Paleae

8–10 mm, 3-toothed.

7–8 mm, apices 3-toothed (middle teeth attenuate, apices purplish, ± hispid).

2n

= 34, 68.

= 34.

Helianthus decapetalus

Helianthus anomalus

Phenology Flowering summer–fall. Flowering spring–fall.
Habitat Mesic to wet woodland edges Sand dunes
Elevation 10–1200 m (0–3900 ft) 1300–1500 m (4300–4900 ft)
Distribution
from FNA
AL; AR; CT; DC; DE; GA; IA; IL; IN; KY; LA; MA; MD; ME; MI; MO; MS; NC; NH; NJ; NY; OH; OK; PA; RI; SC; TN; VA; VT; WI; WV; NB; ON; QC
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from FNA
AZ; UT
[BONAP county map]
Discussion

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.)

L. H. Rieseberg (1991) provided evidence that Helianthus anomalus is a hybrid species derived from H. annuus and H. petiolaris, and subsequent work has confirmed and extended that hypothesis.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 21, p. 158. FNA vol. 21, p. 154.
Parent taxa Asteraceae > tribe Heliantheae > subtribe Helianthinae > Helianthus Asteraceae > tribe Heliantheae > subtribe Helianthinae > Helianthus
Sibling taxa
H. agrestis, H. angustifolius, H. annuus, H. anomalus, H. argophyllus, H. arizonensis, H. atrorubens, H. bolanderi, H. californicus, H. carnosus, H. ciliaris, H. cusickii, H. debilis, H. deserticola, H. divaricatus, H. eggertii, H. exilis, H. floridanus, H. giganteus, H. glaucophyllus, H. gracilentus, H. grosseserratus, H. heterophyllus, H. hirsutus, H. laciniatus, H. laevigatus, H. longifolius, H. maximiliani, H. microcephalus, H. mollis, H. neglectus, H. niveus, H. nuttallii, H. occidentalis, H. paradoxus, H. pauciflorus, H. petiolaris, H. porteri, H. praecox, H. pumilus, H. radula, H. resinosus, H. salicifolius, H. schweinitzii, H. silphioides, H. simulans, H. smithii, H. strumosus, H. tuberosus, H. verticillatus, H. ×laetiflorus
H. agrestis, H. angustifolius, H. annuus, H. argophyllus, H. arizonensis, H. atrorubens, H. bolanderi, H. californicus, H. carnosus, H. ciliaris, H. cusickii, H. debilis, H. decapetalus, H. deserticola, H. divaricatus, H. eggertii, H. exilis, H. floridanus, H. giganteus, H. glaucophyllus, H. gracilentus, H. grosseserratus, H. heterophyllus, H. hirsutus, H. laciniatus, H. laevigatus, H. longifolius, H. maximiliani, H. microcephalus, H. mollis, H. neglectus, H. niveus, H. nuttallii, H. occidentalis, H. paradoxus, H. pauciflorus, H. petiolaris, H. porteri, H. praecox, H. pumilus, H. radula, H. resinosus, H. salicifolius, H. schweinitzii, H. silphioides, H. simulans, H. smithii, H. strumosus, H. tuberosus, H. verticillatus, H. ×laetiflorus
Synonyms H. trachelifolius
Name authority Linnaeus: Sp. Pl. 2: 905. (1753) S. F. Blake: J. Wash. Acad. Sci. 21: 333. (1931)
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