Spanish needles (Bidens pilosa) is well-known as a medicinal herb in the Caribbean, as well as in South America and parts of Africa. In Jamaica, people make a tea from the leaves (or soak the flowers in rum) to treat colds and toothaches. For colic or worms, a mixed infusion prepared from the leaves and roots is traditionally used.

Some people call this plant teething bur and use it to soothe teething babies. In mouthwashes, it helps with sore gums and mouths. The juice of the fresh plant is also applied to cuts, or used as drops for earaches and eye inflammations. The leaves, boiled and eaten like spinach, are said to be good for the bowels and are often added to soup dishes such as callaloo.

Spanish needles grow in damp spots, along pasture margins, and on stream banks. It is native to tropical America, but has spread across all tropical regions and has become one of the world's most widespread weeds.

Its roots are said to ooze chemicals that hinder other plants growing close to it, while its hooked seeds attach easily to clothing and animal fur to help it spread. This plant can be confused with its close relative Bidens alba, though the flowers of that species feature distinct white ray florets.

In laboratory tests, extracts of Spanish needles have been shown to kill malarial parasites, aligning with traditional Amazonian records of its use as an antimalarial remedy. Laboratory research also demonstrates its antibacterial properties.