False daisy

False daisy (Eclipta prostrata) is an annual herb of the aster family (Asteraceae) with prostrate-then-upright, hairy stems 10–50 cm tall, branched from the base. The leaves are opposite, lanceolate to ovate, 2–8 cm long, with toothed margins and rough hairs on both surfaces. The flower heads are small, 6–10 mm across, borne in the leaf axils or at the branch tips; each head has female florets around the outside and bisexual florets in the centre, with white florets and green bracts. A distinctive feature is that the stems and leaves turn dark black when crushed or dried (hence the names "nhọ nồi" and "cỏ mực", meaning "ink weed"). The fruit is small, flattened and dark brown to black. The whole plant contains many active compounds, notably wedelolactone and flavonoids.

False daisy is widespread across the humid tropics and subtropics, growing wild along field margins, ditches, damp ground and lawns; in Vietnam it is found year-round. It is an important herb in traditional medicine: sweet-sour and cooling, it enters the liver and kidney meridians and is used to stop bleeding, tonify the liver and kidney, nourish yin and darken the hair and beard. The famous formula "Erzhi Wan" combines false daisy (mohamilian) with glossy privet fruit to tonify the liver and kidney. Folk uses include a decoction for malaria, dysentery, nosebleeds, haematemesis and menorrhagia; pounded leaves are applied to snakebite, eczema and wounds. Modern research notes the liver-protective, haemostatic and anti-inflammatory activities of its flavonoids and wedelolactone.