- Thin erect, simple, herbaceous, typically single from the base, from a long horizontal rhizome, typically purplish and somewhat glaucous, mostly glabrous but with a few pustulate based hairs directly below the nodes, terete, 2-4mm in diameter at the base, -1m tall, with +/-10 nodes below the flowers.
- Opposite, decussate, sessile or very-short petiolate. Petioles to 2mm long. Blades lanceolate, attenuate, shallow serrate, very scabrous on the top, less scabrous below, rounded at the base, the lowest to +10cm long, +/-2cm broad at the base, with two lateral veins arising from the base of the blade. Teeth of the margins often with a minute white tip.
Adaxial surface of leaf.
Abaxial surface of leaf.
- Single terminal flower head, typically just one per stem.
- -2cm broad in flower, 2.5cm broad in fruit. Phyllaries lanceolate, scabrous externally, glabrous internally, acuminate, to 1cm long and 5mm broad at the base, spreading with the tips ascending, light green, with ciliolate margins, imbricate.
- 8-9 flower per head, sterile. Ligule yellow, oblong, 2.5-3cm long, to 1cm broad, glabrous, acute with a very small single notch at the apex. Corolla tube -1mm long, glabrous. Achenes (in flower) -3mm long. Pappus of ray flowers a pair of serrate awns to 2mm long.
- Disk 1-1.5cm broad in flower, up to 2cm long in fruit. Flowers yellow. Corolla tube 3-4mm long, yellow, mostly glabrous but with some antrorse strigose pubescence externally (mostly in lines), glabrous internally, abruptly contracted at the basal 1mm. Lobes 5, 1-1.3mm long in flower, acute, erect to spreading. Stamens 5, included, adnate at the apex of the constricted portion of the corolla tube. Filaments white glabrous , 3mm long. Anthers maroon 3mm long, connate around the style, mostly included. Style exserted , glabrous, white, bifurcate, +/-5mm long. Stigmas yellow, to +2mm long, pubescent, reflexed. Achenes (in flower) white, glabrous, 3-4mm long. Pappus of 2 awns as in the ray flowers. Awns 2-3mm long. Receptacle hemispheric. Chaff enclosing the disk flowers almost entirely, to -1cm long, glabrous in basal half, pubescent on the margins and apex, slightly yellowish at the apex, acute, with a slightly reddish tip.
- July - October.
- Rocky woods and thickets.
- Native to U.S.
- This species can be found in the eastern-most counties of Missouri (essentially in the counties bordering the Mississippi River). The plant can be identified by its opposite, scabrous, sessile to nearly sessile leaves (which have rounded bases), thin stems, and long rhizomes.
Linnaeus, Sp. Pl. 2: 906. 1753.
, 20—150 cm (rhizomatous)
erect, usually glabrous , rarely ± hairy (often glaucous).
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.
hemispheric, 10—15 mm diam.
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.
5—8 mm, 3-toothed (apices ciliate).
8—12; laminae 15—30 mm.
40+; corollas 4.2—5.5 mm, lobes yellow; anthers usually dark brown to black, appendages yellow.
3—3.6 mm, glabrate;
of 2 aristate scales 2.2—2.5 mm.
One of the earlier flowering perennial
Helianthus, H. divaricatus
resembles the tetraploid
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
. Natural hybrids with
have been named
Small (D. M. Smith and A. T. Guard 1958). Hybrids with other species differ from
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.
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