Bidens pilosa L.
beggar's tick, Spanish needle

This annual to almost perennial shrubby herb forms dense cover along roads, trails and open lowland areas. It is dispersed on human clothing and animal coats. It is not fire tolerant but quickly invades burnt areas. Biological control of this species (a small number of potential agents are known) could be complicated by the presence of endemic species in this genus.

The plant is widely distributed and common in open areas up to 1,300 m. There are several areas on the south slope of Haleakala and the central valley of Maui where carpets of this species inhibit the establishment of native species during the rainy season.

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