The nodding two-tooth (Bidens cernuus) is a species of plant in the composite family (Asteraceae). The herbaceous plant grows as an annual. Height of growth: 20 to 90 cm. The stem is erect and often yellow-green in colour.
Leaves: opposite, stalkless, stem-clasping. The blade is lanceolate. The leaf margin is slightly coarsely toothed. The colour of the leaves is light green, their surface glabrous, or somewhat hairy on the upper side.
The solitary flower heads are about 30 mm in diameter. Especially at fading they begin to "nod". The bracts are arranged in two rows, the outer ones are deciduous and much longer than the inner ones. The tubular flowers are more golden yellow in colour. The flowering period is from July to September.