Capsella

Capsella is a small genus of flowering plants in the family Brassicaceae, comprising several annual or biennial herbs. The best-known species is Capsella bursa-pastoris, commonly called shepherd's purse, a widespread weed in temperate regions.

Description and morphology: Capsella species are typically low-growing plants that form a rosette of leaves in the first year, with slender flowering stems rising above. They produce small, four-petaled flowers arranged in simple clusters. The distinctive fruit is a short, broad silicle (a compact form of a siliqua) that is often triangular or heart-shaped, earning the common name shepherd’s purse in C. bursa-pastoris.

Distribution and habitat: Capsella has a cosmopolitan distribution in temperate zones. Species are commonly found in disturbed soils, including agricultural fields, gardens, roadsides, and waste areas. They are well adapted to early-succession habitats and can spread rapidly.

Ecology and biology: Capsella bursa-pastoris is an annual or winter annual with a prolific seed production. The seeds can persist in the soil seed bank, allowing quick recolonization after disturbance. The genus is closely related to other model and crop relatives in Brassicaceae and is often used in comparative genetics and evolutionary studies.

Taxonomy and relationship: The genus Capsella was described by Carl Linnaeus, with Capsella bursa-pastoris designated as the type species. Capsella is closely related to Arabidopsis and other genera within Brassicaceae, sharing many morphological and genetic characteristics.

Species overview: In addition to C. bursa-pastoris, Capsella includes several other regional species, recognized differently across taxonomic sources. These species vary in distribution and habitat preference, but all share the characteristic purse-shaped fruit and small white flowers.