Silphium asteriscus L.
Family - Asteraceae
Stems - To +1m tall, simple to branching near apex, erect, herbaceous, hirsute to hispid-scabrous, from caudex and thick roots and rhizomes.
Leaves - Alternate, short petiolate below, sessile above. Blades lanceolate, to +15cm long, +4cm broad, coarse serrate, acute, scabrous and pubescent above, pubescent below. Upper leaves rounded at base. Lower leaves with leaf tissue tapering at base and creating a winged petiole. Teeth of margins with minute whitish apex.
Inflorescence - Terminal flower heads in a compact corymbiform cluster. Peduncles to +/-2cm long, hirsute to hispid.
Involucre - To +1cm tall, +1.5cm in diameter. Phyllaries imbricate, ovate-lanceolate, acuminate, to 1.5cm long, +6mm broad, spreading to recurved, pubescent to hispidulous.
Ray flowers - Fertile, typically 9 or 10. Ligules yellow, to 2.5cm long, 1cm broad, narrowly elliptic to narrowly oblong, with small notch at apex, glabrous. Achenes compressed, winged, 5-6mm long, 3mm broad (in flower), mostly glabrous but with cilia on margins near apex, becoming black in fruit. Pappus absent.
Disk flowers - Disk yellow, +/-1.1cm in diameter. Flower staminate. Corolla tubes to 5-6mm long, yellow, glabrous, 5-lobed. Lobes glandular pubescent. Style yellow, undivided, well exserted. Achenes white, terete, glabrous, 5-6mm long. Pappus absent. Receptacle flat. Chaff 1cm long, 2mm broad, yellowish and acute at apex, pubescent above with some glandular hairs.
Arrow showing the undivided style of the disk flower.
Flowering - May - September.
Habitat - Rocky open woods, glades, roadsides.
Origin - Native to U.S.
Other info. - This plant
can be found in the southern-most counties of Missouri.
Photographs taken at the Peck Ranch Wildlife Refuge, Carter County, MO., 6-12-03.