Mohr's Thoroughwort

As treated here, Eupatorium mohrii includes both sexual diploid (sometimes segregated as E. recurvans) and apomictic polyploid populations that are suggested by molecular data to be autoploids. Eupatorium saltuense refers to hybrids shown by molecular data to involve E. mohrii and E. serotinum. Molecular data also document frequent hybridization with E. rotundifolium.

Perennials, 30–100+ cm. Stems (from tuberous rhizomes) multiple, densely branched distally, puberulent throughout. Leaves usually opposite (distal sometimes alternate); sessile or subsessile; blades 3-nerved distal to bases, oblanceolate, 20–80 × 5–10(–20) mm, bases cuneate, margins serrate proximally, entire distally, apices acute, faces puberulent (abaxial), glabrous or glabrate (adaxial), gland-dotted. Heads in corymbiform arrays. Phyllaries 7–10 in 1–2 series, oblanceolate, 1–3 × 0.2–0.5 mm, apices rounded, abaxial faces puberulent, gland-dotted. Florets 5; corollas 2–4 mm. Cypselae 1–2 mm; pappi of 20–30 bristles 2.5–3 mm. 2n = 20, 30, 40.

Eupatorium recurvans Small

Eupatorium mohrii, commonly called Mohr's thoroughwort, is a herbaceous perennial plant in the family Asteraceae native to the southeastern and south-central states of the United States, in the coastal plain from Virginia to Texas. It has also been found in the Dominican Republic.

Eupatorium mohrii is a perennial herb up to 100 cm (40 inches) tall and are producing tuberous rhizomes. As with other species of Eupatorium, the inflorescences contain a large number of tiny white flower heads, each with 5 disc florets but no ray florets. It forms hybrids with Eupatorium serotinum and Eupatorium rotundifolium.

Eupatorium mohrii grows in moist areas, edges of ponds, and sandy soils.