Bidens is a genusin the family Asteraceae. It contains about 200 species. The common names beggarticks, bur-marigolds, stickseeds, tickseeds and tickseed sunflowers refer to the achene burrs on the seeds of this genus, most of which are barbed. The generic name refers the same fact; it means "two-tooth", from Latin bis "two" + dens "tooth".
The plants are zoochorous; their seeds will stick to clothing, fur or feathers, and be carried to new habitat. This has enabled them to colonize a wide range, including many oceanic islands. Some of these species occur only in a very restricted range and several are now threatened with extinction, notably in the Hawaiian Islands. Due to the absence of native mammals on these islands, some of the oceanic island taxa have reduced burrs, evolving features that seem to aid in dispersal by the wind instead.
Smooth Beggarticks (B. laevis) is a common fall flower in the southeastern USA. Pitchfork Weed (B. frondosa) is considered to be a weed in New Zealand, although it is not officially declared an invasive species.