|Scientific Name||Bidens pilosa|
|Common Names||English: Common blackjack, Spanish needle; German: Behaarter Zweizahn; French: Bident poilu|
|Description||Annual, seed-propagated weed, forms a dense ground cover.|
Ray florets absent or 4-7 per head, rays 2-8 mm (0.079 - 0.31 inch) long.
Lanceolate, striped lengthwise, with reddish hypocotyl.
Erect, ramified, square, hairless, up to 120 cm (47.24 inch) high.
Petiolate, with 1-2 pairs of petiolate pinnae and a large terminal pinna.
Flower heads longer than wide, with yellow disk florets and white ray florets.
Achenes dark brown or black, straight, wingless, 8-16 mm (0.31 - 0.63 inch) long, setose.
Germination in spring.
Viability of Seeds
By seed. Seeds attach to clothing or animal fur or feathers. B. pilosa is also dispersed by water. Ca. 3,000-6,000 seeds/plant.
Pastures, plantations, along roadsides and on wasteland.
Moist, nutrient-rich, warm regions.
Major weed in vegetables, forms a dense ground cover that prevents regeneration of other species.
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