Bidens L.

Most leaves cauline Bidens
Leaves divided pinnatisectly into 3 segments; terminal segment 6–8 cm long, 2 cm wide; lateral segments half as large; all coarsely toothed. Herb up to 1 m high, with a single erect stem with few or no branches. Heads terminal and axillary. Involucral bracts 1–2 cm diam. Ray yellow. Cypselas 6–8 mm long. Pappus awns 2–4 mm long, finely barbed. Coast. Near habitation. Introd. from America. Fl. autumn–winter. Burr Marigold Bidens tripartita
Leaves pinnately divided into 3–5 segments or pinnatisectly into 5 or more segments; the lower ones sometimes simple. Cypselas up to 12 mm long, 4-angled. Pappus awns up to 3 mm long