21.
Helianthus divaricatus
Linnaeus, Sp. Pl. 2: 906. 1753.
Woodland sunflower
Helianthus divaricatus
var.
angustifolius
Kuntze
Perennials
, 20—150 cm (rhizomatous)
. Stems
erect, usually glabrous , rarely ± hairy (often glaucous).
Leaves
cauline; opposite; sessile; blades (light to dark green, sometimes whitish abaxially, 3-nerved at bases) lanceolate to lance-ovate, 6—15 × 1—5 cm, bases rounded to cordate, margins subentire to serrate, abaxial faces sparsely hispid to hispidulous, gland-dotted.
Heads
1—10.
Peduncles
0.5—9 cm.
Involucres
hemispheric, 10—15 mm diam.
Phyllaries
18—25, lanceolate, lance-linear, or lance-ovate, 6—12 × 2—2.5 mm, (margins ciliate) apices acuminate to attenuate, abaxial faces hispidulous to glabrate, not gland-dotted.
Paleae
5—8 mm, 3-toothed (apices ciliate).
Ray florets
8—12; laminae 15—30 mm.
Disc florets
40+; corollas 4.2—5.5 mm, lobes yellow; anthers usually dark brown to black, appendages yellow.
Cypselae
3—3.6 mm, glabrate;
pappi
of 2 aristate scales 2.2—2.5 mm.
2
n
= 34.
Flowering summer—early fall. Dry, open sites; 10—900+ m; Ont., Que.; Ala., Ark., Conn., Del., D.C., Fla., 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.
One of the earlier flowering perennial
Helianthus, H. divaricatus
resembles the tetraploid
H. hirsutus
but differs by its usually glabrous and often glaucous stems, sessile or subsessile leaves, and smaller reproductive organs (disc corollas, paleae, cypselae). Plants from the Ozark region of Arkansas have larger leaves and heads and may represent a polyploid form of
H. divaricatus
. Natural hybrids with
H. microcephalus
have been named
H
.
glaucus
Small (D. M. Smith and A. T. Guard 1958). Hybrids with other species differ from
H. divaricatus
in having short but distinct petioles, hairy stems, leaves with more rounded bases, and primary lateral leaf veins diverging in a subopposite manner distal to bases, rather than being strictly opposite and basal.
