Helianthus grosseserratus Martens

Helianthus grosseserratus plant

Family - Asteraceae

Stems - Erect, herbaceous but stout, from stout thickened roots, to +2m tall, glabrous, glaucous, terete, purple in strong sun, single from the base, typically simple below the inflorescence, with some antrorse strigose hairs in the inflorescence, typically 5-6(10)mm in diameter.

Helianthus grosseserratus stem

Helianthus grosseserratus rootRoot.

Leaves - Opposite, alternate in the upper stems, petiolate. Petioles to +/-2.5cm long, slightly winged by decurrent leaf tissue, glabrous (mostly below), with arachnoid hairs on the adaxial side of the upper stems. Blades linear-lanceolate, to +20cm long, -3cm broad, typically folded, with coarse shallow teeth, attenuate, scabrous and dark green adaxially, pale greenish-white and with dense matted hairs abaxially. Veins expressed below. Main veins anastomosing about 1-2mm before the edge of the leaf.

Helianthus grosseserratus leavesFolded nature of the leaves.

Helianthus grosseserratus leaves

Inflorescence - Single flower head terminating axillary and branches. Peduncles antrorse strigose, typically with one or two linear bracts.

Involucre - To +1.5cm broad, 1cm tall. Phyllaries long attenuate, spreading in the apical 1/2 to 2/3, green, with densely antrorse ciliolate margins, otherwise mostly glabrous on the surface, sparse pubescent internally or not, to 1.5cm, 2-3mm broad at the base, somewhat viscid.

Helianthus grosseserratus involucreInvolucre...

Helianthus grosseserratus involucre...again.

Ray flowers - +/-16 per head, sterile. Corolla tube +/-2mm long, antrorse pubescent, yellow. Ligule to 3cm long, -1cm broad, glabrous except at the base abaxially, yellow. Achene (in flower) white, 3.5mm long, 3-sided, glabrous, with one or two awned scale(s). Scales to -2mm long (including awn).

Helianthus grosseserratus flowers

Disk flowers - Disk to 1.5cm broad. Corollas yellow, constricted in the basal 1/4, antrorse pubescent externally, glabrous internally, 6mm long, 5-lobed. Lobes yellow, erect, acute, 1.3mm long. Stamens 5, adnate at the apex of the constricted portion of the corolla tube. Filaments compressed, pale yellow, 3-4mm long. Anthers dark purple-brown, 2.5mm long, exserted, connate around style. Style exserted beyond the anthers, bifurcate, pale basally, yellow apically, glabrous, divided for about 2mm. Achenes white in flower, 4mm long, glabrous, 3-sided. Awns 2, white, lanceolate, 2-2.2mm long, .5mm broad at the base. Receptacle slightly conic to convex. Chaff translucent but green at the apex, to 1cm long, acute, ciliolate at the apex, to 1.5mm broad, partially folded around the disk florets. Achenes black at maturity, glabrous.

Helianthus grosseserratus disk

Flowering - July - October.

Habitat - Prairies, low meadows, moist thickets, fields, ditches, roadsides, railroads.

Origin - Native to U.S.

Other info. - This showy species can be found throughout much of Missouri but is apparently absent from most of the southeastern 1/3 of the state. The plant is easy to ID in the field because of its fairly thin, slightly folded, leaves and its glabrous and glaucous stems. No other species of sunflower in Missouri has this combination of leaf shape and stem pubescence. The plant is very common, especially in the western part of the state.

Photographs taken outside of Salem, MO. off Hwy 68, 9-18-03, and at Tall Grass Prairie, KS., 9-23-06.


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