Capsella bursa-pastoris, known as shepherd's purse because of its triangular flat fruits, which are purse-like, is a small annual and ruderal flowering plant in the mustard family . It is native to eastern Europe and Asia minor, but is naturalized and considered a common weed in many parts of the world, especially in colder climates, including British Isles, where it is regarded as an archaeophyte, North America and China, but also in the Mediterranean and North Africa. C. bursa-pastoris is the second-most prolific wild plant in the world, and is common on cultivated ground and waysides and meadows.
Scientists have referred to this species as a 'protocarnivore', since it has been found that its seeds attract and kill nematodes as a means to locally enrich the soil.