Eupatorium serotinum Michx.
Family - Asteraceae
Stems - To 2m tall, pubescent above, glabrescent below.
Leaves - Opposite, toothed, petiolate, acuminate, ovate to lanceolate, to +15cm long, 10cm broad, typically glabrous.
Inflorescence - Terminal corymbiform clusters with many flower heads. Flower heads with +/-15 flowers.
Involucre - +/-5mm long(tall). Phyllaries imbricate, obtuse or rounded, pubescent.
Ray flowers - Absent.
Disk flowers - Disk florets 9-15 per head. Corolla white to grayish-lavender, 5-lobed. Pappus of capillary bristles. Achenes black when mature.
Flowering - August - October.
Habitat - Pastures, prairies, waste ground, disturbed sites, roadsides, railroads.
Origin - Native to U.S.
Other info. - One of the most common "weeds" in the state, this plant is a dominant presence of the landscape when in full bloom. It is a pioneering plant and thrives in areas which get cut or mowed on occasion. It is definitely the most common Eupatorium in Missouri.
Photographs taken off Hwy 60, Carter County, MO., 8-28-03 (DETenaglia); also near Fremont, MI, 9-22-2012 (SRTurner).