Bayer - Bidens Pilosa

Annual, seed-propagated weed, forms a dense ground cover. English: Common blackjack, Spanish needle; German: Behaarter Zweizahn; French: Bident poilu

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Characteristic Features

Ray florets absent or 4-7 per head, rays 2-8 mm (0.079 - 0.31 inch) long.

Cotyledons

Lanceolate, striped lengthwise, with reddish hypocotyl.

Stems

Erect, ramified, square, hairless, up to 120 cm (47.24 inch) high.

Leaves

Petiolate, with 1-2 pairs of petiolate pinnae and a large terminal pinna.

Propagation Organs

Flowers

Flower heads longer than wide, with yellow disk florets and white ray florets.

Flowering Period

Summer.

Fruit

Achenes dark brown or black, straight, wingless, 8-16 mm (0.31 - 0.63 inch) long, setose.

Seeds

Germination in spring.

Viability of Seeds

3-5 years.

Propagation

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.

Occurrence

Habitat

Pastures, plantations, along roadsides and on wasteland.

Soil

Moist, nutrient-rich, warm regions.

Agricultural Importance

Major weed in vegetables, forms a dense ground cover that prevents regeneration of other species.

Descriptions