Semaphore thoroughwort

Perennials, 50–100+ cm. Stems (from short rhizomes, green) single, branched distally, puberulent throughout. Leaves opposite (± vertical); petiolate (petioles 10–30 mm); blades ± 3-nerved distal to bases, deltate to rhombic, 25–80 × 20–60 mm, bases broadly cuneate, margins usually serrate (teeth uneven), sometimes crenate, apices acute, faces glabrate to sparsely puberulent, gland-dotted. Heads in corymbiform arrays. Phyllaries 8–12 in 2–3 series, elliptic to oblong, 1.5–5 × 0.8–1 mm, apices acute to acuminate, abaxial faces puberulent, gland-dotted. Florets 5; corollas 3.5–4 mm. Cypselae 1.2–1.5 mm; pappi of 20–35 bristles 3.5–4.5 mm. 2n = 20.

Flowering Jul–Sep. Moist or wet, low, often saline places; 0–10+ m; Fla.