27.
Helianthus strumosus
Linnaeus, Sp. Pl. 2: 905. 1753.
Rough sunflower, hélianthe scrofuleux
Helianthus montanus
E. Watson;
H. saxicola
Small
Perennials
, 100—200 cm (rhizomatous).
Stems
erect, glabrous or glabrate.
Leaves
cauline; mostly opposite, sometimes alternate (distal); petioles 1—3 cm; blades (light to dark green, 3-nerved distal to bases) lanceolate to lance-ovate or ovate, 7—18 × 2—10 cm, bases subcordate to ± cuneate, margins entire to ± serrate, abaxial faces glabrous or tomentulose, usually densely gland-dotted.
Heads
3—15.
Peduncles
1—9 cm.
Involucres
cylindric to hemispheric, 8—20 mm diam.
Phyllaries
18—25 (erect, loose, or squarrose), lanceolate, 5.5—10 × 1.5—3 mm (equaling or slightly surpassing discs), (margins usually ciliate) apices acute to acuminate, abaxial faces glabrous or hispidulous, usually not gland-dotted.
Paleae
5.3—6.5 mm, 3-toothed.
Ray florets
10—20; laminae ca. 12—20(—30) mm.
Disc florets
35+; corollas 5.5—6.5 mm, lobes yellow; anthers dark, appendages dark or reddish brown.
Cypselae
4—5.5 mm, glabrate;
pappi
of 2 aristate scales (1—)2—2.5 mm.
2
n
= 68, 102.
Flowering late summer—fall. Woods , roadsides, prairies; 0—1500 m; Ont., Que.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va., Wis.
Helianthus strumosus
is variable, particularly for leaf shape and indument; sufficient study has not been undertaken to evaluate whether regional forms deserve taxonomic recognition. Hybridization with other polyploids, including
H. decapetalus, H. hirsutus
, and
H. tuberosus
, further complicates the situation. It differs from
H. tuberosus
in having glabrous (or glabrate) stems and in lacking tubers.
