Japanese name: コセンダングサ（小栴檀草） Scientific name:Bidens pilosa var. pilosa
[Overview]
An annual 50–110 cm tall, found along roadsides and in vacant lots.
The stem is erect, branched, 4–6-ridged, and covered with short hairs.
The leaves are pinnately compound, 10–14 cm long, opposite on the lower part of the stem and alternate on the upper part, and consist of 3–5 leaflets.
Some leaves on the upper part of the stem are not pinnately compound but are 3-lobed or simple and lanceolate.
The leaf margins are serrated.
Flower heads are borne at the branch tips on the upper part of the stem and usually have no ray florets.
The outer involucral bracts are spoon-shaped with widened tips, 7–8 in number.
The fruit is an achene with 2–4 awns (spines).
The awns have small downward-pointing barbs.
[History]
It arrived in Japan in the Edo period and has naturalized from Honshu southward.
[Uses]
The whole plant is used medicinally.
[Notes]
It is designated as an invasive alien species requiring caution under the Invasive Alien Species Act.
