1. Mikania scandens (L.) Willd. (climbing hempweed)

M. pubescens Nutt.

Pl. 270 h, i; Map 1130

Plants perennial twining herbs, with fleshy, clustered roots. Stems prostrate or more commonly climbing in other vegetation, 1–5 m long, densely and minutely hairy to nearly glabrous, often also sparsely glandular. Leaves opposite (the nodes well separated), long-petiolate. Leaf blades 2–12 cm long, triangular to triangular-ovate, truncate to cordate at the base, tapered to a sharply pointed tip, often with a pair of short, bluntly triangular, spreading basal lobes, the margins otherwise entire to somewhat wavy, scalloped or bluntly toothed, the surfaces sparsely to moderately pubescent with short, curved hairs, also sparsely to moderately glandular, the main veins palmate. Inflorescences axillary panicles or stalked clusters, dome-shaped. Heads with 4 disc florets. Involucre 4–6 mm long, more or less cylindrical, the bracts 4 (the head often also subtended by 1 or 2 other shorter bracts), more or less equal in size, narrowly oblong-elliptic to narrowly elliptic-lanceolate, tapered to a sharply pointed tip, glabrous or sparsely to moderately and finely short-hairy. Receptacle flat or nearly so. Corollas white to pale pink or rarely pale lavender, glandular. Pappus of numerous capillary bristles. Fruits 1.5–2.5 mm long, 5-angled, somewhat wedge-shaped in profile (usually slightly and unevenly tapered at the base) to nearly linear, densely glandular, dark brown to black. 2n=38. July–October.

Scattered in the Mississippi Lowlands Division (eastern [mostly southeastern] U.S. west to Michigan, Missouri, and Texas; Canada, Mexico, Caribbean Islands). Swamps, bottomland forests, banks of oxbows and sloughs, and margins of lakes and ponds; also ditches, levees, fencerows, and roadsides.