Compositae

Compositae, commonly known as the aster family or Asteraceae, is one of the largest families of flowering plants, with roughly 23,000 species in over 1,600 genera. Members are cosmopolitan, occurring in nearly all habitats from deserts to high mountains, though diversity is especially high in the Americas and Africa. The group includes herbs, shrubs, and a few trees, as well as many ornamentals and crops.

A defining feature is the inflorescence: a capitulum (flower head) that gathers many small flowers (florets) into a single composite inflorescence. Florets may be only disk florets, only ligulate ray florets, or both kinds. The head is typically subtended by an involucre of bracts called phyllaries. After fertilization, the fruit is usually a cypsela, and most species bear a pappus of hairs, scales, or similar structures that aids wind dispersal.

Ecology and economic importance: Members are important nectar sources for pollinators and often dominate open habitats. Agriculturally, the family includes lettuce (Lactuca sativa), sunflower (Helianthus annuus), chicory (Cichorium intybus), artichoke (Cynara cardunculus), and many ornamentals such as dahlias, chrysanthemums, and marigolds. The group also includes numerous wild species used in traditional medicines and as landscape plants.

Taxonomy and evolution: Historically the group was called Compositae; modern classifications typically use Asteraceae. The family is divided into multiple subfamilies and tribes, with Asteroideae being the largest. Molecular phylogenetics has clarified many relationships within the group, yet the defining features—the composite head, phyllaries, and often a pappus—remain central for identification.