View photos of the medicinal plant Bidens sambucifolia (Tickseed).

View photos of the medicinal plant Bidens pilosa (Spanish needles), profiled in Medicinal Plants of the American Southwest.

A passage from Medicinal Plants of the American Southwest:

Spanish needles is used as a treatment in some areas of the tropical world where malaria is problematic. This plant (and other species, such as Bidens frondosa, B. bipinnata, and B. ferulaefolia) has been found to retard the growth of Plasmodium falciparum, one of the main parasites responsible for malaria. Spanish needles is used advantageously as a co–therapy with pharmaceuticals where drug resistance is an issue.

View photos of the medicinal plant Bidens aurea (Apache beggarticks).