Japanese name: アメリカセンダングサ Scientific name:Bidens frondosa
[Overview]
An annual 1–1.5 m tall, found along roadsides and at the edges of ditches, preferring slightly moist places.
The whole plant is tinged with purplish brown.
The stem is erect, much branched, 4-ridged, and almost hairless.
The leaves are opposite and pinnately compound, consisting of 3–5 leaflets.
The leaflets are ovate-lanceolate, 3–13 cm long, with distinct leaflet stalks and serrated margins.
The leaves are almost hairless.
Flower heads are borne at the branch tips on the upper part of the stem, with inconspicuous ray florets.
The outer involucral bracts are leaflike, 2–3.5 cm long, 6–12 in number.
The fruit is a flattened achene with 2 awns (spines).
The awns have small downward-pointing barbs.
[History]
It arrived in Japan in the Taisho era and has naturalized throughout the country.
