Helianthus decapetalus

Linnaeus

Sp. Pl. 2: 905. 1753.

Common names: Thinleaf sunflower hélianthe à dix rayons
Endemic
Synonyms: Helianthus trachelifolius Miller
Treatment appears in FNA Volume 21. Treatment on page 158. Mentioned on page 146, 159.

Perennials, 60–200 cm (rhizomatous). Stems erect, glabrous. 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 glanddotted. Heads 3–6 (–10). Peduncles 2–12 cm (not glanddotted). Involucres hemispheric, 12–25 mm diam. 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 glanddotted. Paleae 8–10 mm, 3-toothed. Ray-florets 8–12; laminae 20–25 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. Cypselae 3.5–5 mm; pappi of 2 aristate scales 3–4 mm. 2n = 34, 68.


Phenology: Flowering summer–fall.
Habitat: Mesic to wet woodland edges
Elevation: 10–1200 m

Distribution

V21-377-distribution-map.gif

N.B., Ont., Que., Ala., Ark., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Ky., La., Maine, Md., Mass., Mich., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Vt., Va., W.Va., Wis.

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.

Selected References

None.

Lower Taxa

None.
... more about "Helianthus decapetalus"
strigillose +  and glabrate +
not tailed +, rounded +  and obtuse +
usually dark-brown +  and black +
pale +  and dark +
connate +  and distinct +
subequal +
scarious +
usually ovate +  and lanceolate +
reddish-brown +  and dark +
usually deltate +  and lanceolate +
spiciform +, paniculiform +  and corymbiform +
indeterminate +  and determinate +
Edward E. Schilling +
Linnaeus +
rounded +  and cuneate +
7 cm70 mm <br />0.07 m <br /> (21 cm210 mm <br />0.21 m <br />) +
lanceolate;ovate +
4cm;10cm +
winged;ribbed;winged;ribbed +
tuberculate +  and rugose +
barbellulate +  and barbellate +
Thinleaf sunflower +  and hélianthe à dix rayons +
reddish +  and yellow +
0.65 cm6.5 mm <br />0.0065 m <br /> (0.72 cm7.2 mm <br />0.0072 m <br />) +
hairy +  and glabrous +
compressed +  and obpyramidal +
fertile +  and bisexual +
fertile +  and bisexual +
N.B. +, Ont. +, Que. +, Ala. +, Ark. +, Conn. +, Del. +, D.C. +, Ga. +, Ill. +, Ind. +, Iowa +, Ky. +, La. +, Maine +, Md. +, Mass. +, Mich. +, Miss. +, Mo. +, N.H. +, N.J. +, N.Y. +, N.C. +, Ohio +, Okla. +, Pa. +, R.I. +, S.C. +, Tenn. +, Vt. +, Va. +, W.Va. +  and Wis. +
10–1200 m +
hairy +  and glabrous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Mesic to wet woodland edges +
in more or less corymbiform , paniculiform or spiciform , arrays +  and singly +
indeterminate +
homogamous +  and heterogamous +
each +  and sessile +
1.2 cm12 mm <br />0.012 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
hemispheric +
2 cm20 mm <br />0.02 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
sessile +  and petiolate +
alternate +  and opposite +
triangular +
2-carpellate +
3-toothed +
0.8 cm8 mm <br />0.008 m <br /> (1 cm10 mm <br />0.01 m <br />) +
persistent +
coroniform +
2 cm20 mm <br />0.02 m <br /> (12 cm120 mm <br />0.12 m <br />) +
1 cm10 mm <br />0.01 m <br /> (2 cm20 mm <br />0.02 m <br />) +
2 cm20 mm <br />0.02 m <br /> (5 cm50 mm <br />0.05 m <br />) +
Flowering summer–fall. +
1.1 cm11 mm <br />0.011 m <br /> (1.6 cm16 mm <br />0.016 m <br />) +
20 +  and 25 +
0.2 cm2 mm <br />0.002 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
bearing subulate enations +, hairy +  and bristly +
flat;slightly convex +
aristate +
0.3 cm3 mm <br />0.003 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
exalbuminous +
procumbent +  and decumbent +
appendaged +  and truncate +
hirsutulous +  and glabrous +
papillate +
Helianthus trachelifolius +
Helianthus decapetalus +
Helianthus +
species +
campanulate +
toothed +  and entire +
300 cm3,000 mm <br />3 m <br /> (500 cm5,000 mm <br />5 m <br />) +
60 cm600 mm <br />0.6 m <br /> (200 cm2,000 mm <br />2 m <br />) +
shrub +  and subshrub +