Helianthus salicifolius A. Dietr. - Willow-leaf Sunflower

Helianthus salicifolius plant

Family - Asteraceae

Stems - Erect, typically simple until the inflorescence, terete, herbaceous, to +2m tall, typically 4-7mm broad at the base, glaucous, from elongate horizontal rhizomes and forming large colonies.

Helianthus salicifolius stem

Leaves - Alternate, sessile, dense in the middle of the stem, spread apart more in the apical 1/3 of the plant, typically dried and deciduous in the basal 1/3 of the plant at anthesis, thin, glabrous, typically conduplicate, to +10cm long, 1-3mm broad, falcate.

Helianthus salicifolius leaves

Inflorescence - Open, corymbose arrangement of flower heads on long peduncles. Peduncles glabrous, with a few reduced bracts, 5-20cm long.

Helianthus salicifolius inflorescence

Involucre - +1cm broad and tall, of imbricate phyllaries. Phyllaries long attenuate, 1-1.5cm long, 2-3mm broad at the base, mostly glabrous but with spreading hairs at the base and appressed hairs along the margins, viscid externally.

Helianthus salicifolius involucre

Ray flowers - +/-12 per head. Ligules yellow, +/-2.5cm long, 7-10mm broad, elliptic, glabrous. Corolla tube 2mm long, glabrous. Pappus of +/-5 translucent arista. Arista 1-3mm long.

Helianthus salicifolius flowers

Disk flowers - Disk +/-1cm broad. Corolla tube +/-5mm long, slightly glandular at the base externally, yellow, glabrous internally, +/-1mm in diameter, 5-lobed. Lobes purplish-brown, 1mm long, acute, glabrous. Stamens 5, adnate at the base of the corolla tube. Filaments yellow, glabrous, 2-3mm long. Anthers 3-4mm long, mostly exserted, connate around the style and stigma. Styles bifurcate at the apex, mostly glabrous but pubescent on the stigmas, yellow. Stigmas +/-2mm long, recurved. Receptacle chaffy. Chaff to -1cm long, folded around the disk florets, pubescent and translucent in the basal 2/3, greenish and puberulent in the apical 1/3, acute. Mature achenes not seen.

Helianthus salicifolius disk

Flowering - August - October.

Habitat - Upland prairies, limestone glades, roadsides.

Origin - Native to U.S.

Other info. - This attractive species can be found in a handful of western Missouri counties. The plant is easy to identify becasue of its thin, dense, falcate leaves. The leaves are congested at the middle of the stem at anthesis.
H. salicifolius would make a great garden subject as it forms large colonies and the plants attain a tall height when mature. Each plant produces many medium-sized flower heads.

Photographs taken at Tall Grass Prairie National Preserve, KS., 9-18-06.


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