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.

Leaf or leaflet blades about 6-12 x 4-8 cm, only sparsely hairy on the underside, usually trifoliate or pinnate, occasionally simple. Petioles grooved on the upper surface, petiole bases forming a transverse ridge across the twig and this ridge resembles a stipular scar. Stems +/- 4-angled.

Flowers borne in heads about 5-15 mm diam., about 40-50 flowers per head. Flowers surrounded or subtended by persistent erect bracts with fimbriate margins. Pollen orange.

Each fruit or nutlet about 6-12 mm long, ending in about 3-5 plumes each with downward pointing hairs which adhere to clothes, animal fur, etc. Cotyledons longer than the radicle but of equal width.

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.

A cosmopolitan species of uncertain origin, now naturalised in WA, NT, CYP, NEQ, CEQ and southwards as far as Victoria. Altitudinal range from near sea level to 1200 m. Grows in disturbed areas in rain forest.

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).