Helianthus strumosus L.

Helianthus strumosus plant

Family - Asteraceae

Stems - To 2m tall, simple, glabrous( but sometimes scabrous in inflorescence), erect, from thick rhizomes, greenish below, purple above.

Leaves - Opposite, petiolate, shallow toothed to entire, lanceolate, scabrous, to +5cm broad, +15cm long, acuminate at apex, stigilose on margins, rounded to tapering at base. Petioles to +1.5cm long.

Helianthus strumosus leaves

Inflorescence - Single flower heads on short peduncles from upper leaf axils.

Involucre - To -1cm tall(long), 1.5cm in diameter. Phyllaries imbricate, attenuate, with spreading tips, innermost phyllaries to 1.6cm long, 4mm broad at base, glabrous with strigillose or minutely fimbriate margins.

Helianthus strumosus involucreInvolucre.

Ray flowers - Ligule yellow, to +3cm long, 1cm broad, sparse pubescent externally, glabrous internally. Flower sterile. Achene white in flower, 3.3mm long, glabrous, 3-sided. Pappus of 2 short awns to 1mm long.

Disk flowers - Disk to 1.6cm in diameter. Corolla yellow, 5-lobed. Corolla tube to 4mm long, scabrous. Lobes 1.2mm long, acute. Style bifurcate, pubescent at apex (stigma). Stamens 5, adnate at base of corolla tube. Anthers brownish-black, 3.5mm long, connate around style. Achenes to +4mm long, glabrous. Pappus a pair of awns to 2mm long. Receptacle slightly convex. Chaff to 1cm long, white below, yellow at apex, 3-lobed at apex, with large acute central lobe and two small rounded side lobes. All lobes fimbriate.

Helianthus strumosus flower

Flowering - July - September.

Habitat - Low woods, thickets, open woods, prairies, wet meadows, roadsides, railroads.

Origin - Native to U.S.

Other info. - Some of the sunflowers, genus Helianthus, can be very hard to distinguish from one another. H. strumosus is no exception. The plant greatly resembles another, H. hirsutus, and the two are probably indistinct. For more on this read the notes on the H. hirsutus page.
H. strumosus is fairly common in the state but not as common as other species in the genus such as H. annuus L., H. mollis Lam., or H. grosseserratus Martens.

Photographs taken on Garrison Ridge, Mark Twain National Forest, Christian County, MO.,7-28-00.


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