Eupatorium sessilifolium L.
Family - Asteraceae
Stem - Erect, to 1.2 m, glabrous below inflorescence, not hollow.
Stem and leaves.
Lower stem and node.
Upper stem and node.
Leaves - Leaves opposite, sessile, rarely with petioles to 2 mm, blades with single midvein, narrowly ovate with toothed margins, bases rounded to truncate, with antipodal leaves often overlapping at base. Axillary fascicles absent. Leaf surfaces glabrous, gland-dotted.
Inflorescence - Terminal panicles, +/- flat-topped.
Involucre - To 6.5 mm long, narrowly cup-shaped. Involucral bracts densely short-hairy, green.
Florets - Usually 5 per head. Corollas 3-4 mm long, white, surfaces often glandular. Styles well exserted at anthesis. Pappus of numerous capillary bristles.
Flowering - July - September.
Habitat - Forests, bluffs, streambanks.
Origin - Native to the U.S.
Other info. - This plant is a little less common than some of the more weedy members of the genus. It is found mainly in the Ozark region and also the eastern portion of the Glaciated Plains. It often grows as an understory plant. Missouri plants have relatively long, narrow leaves, and have been called var. brittonianum by some authors; however, the degree of intergradation argues against formal taxonomic recognition of these infraspecific forms.
Photographs taken at Cuivre River State Park, Lincoln County, MO, 9-29-2012 and 8-15-2014 (SRTurner).