Bidens pilosa L.
Linnaeus, C. von (1753) Species Plantarum 2: 832. Type: Habitat in America.
Spanish Needles; Beggar Ticks; Pitchforks; Cobbler's Pegs; Blackjack
Annual herb, but occasionally grows into a shrub 1.7 m tall.
Cotyledons +/- linear, about 13-22 x 2-4 mm. First pair of leaves either simple or deeply lobed or compound with three leaflets each of which is toothed or lobed. At the tenth leaf stage: leaves trifoliolate with the middle leaflet much longer than the lateral leaflets. Leaflets hairy on both the upper and lower surfaces. Seed germination time 12 to 33 days.
Two varieties occur, see Flora of Australia 37:460-462.
This species has medicinal uses. An infusion of the plant, sometimes of the flower-heads only, has been used in domestic medicine in several countries for diarrhoea, dysentery and coughs; the tannin content provides an astringency which would be of some use in those complaints. Cribb (1981).