Acanthaceae

Acanthaceae is a family of flowering plants in the order Lamiales. It comprises roughly 230 to 250 genera and about 4,000 species, with a distribution centered in tropical and subtropical regions and a number extending into temperate zones. The group includes herbs, shrubs, and climbing plants, many of which are cultivated for their ornamental flowers. The family shows considerable diversity in form and habit.

Characteristic features include opposite or whorled leaves with simple margins, and often conspicuous stipules. Inflorescences are typically spikes, racemes, or panicles bearing flowers that are frequently tubular or two-lipped. The flowers are adapted for insect or bird pollination in many genera. The calyx is usually five-lobed, and the fruit is commonly a capsule that dehisces to release seeds. Bracts and colorful calyces are common in many decorative species.

Ecology and uses: Acanthaceae species occupy a wide range of habitats, from rainforest understories to open savannas and moist edges. They are primarily pollinated by bees and other insects, though some species attract hummingbirds or other pollinators. Many genera are valued horticulturally, including Acanthus, Justicia, Ruellia, and Thunbergia, with popular ornamentals such as Thunbergia grandiflora and Ruellia simplex. The aquatic genus Hygrophila is widely used in freshwater aquariums. Ethnobotanical uses vary by region, with some species employed in traditional medicine.

Taxonomy and terminology: The family is placed within Lamiales and has been subdivided into several subfamilies, though circumscription varies among classifications. The name Acanthaceae derives from Greek acantha, “thorn,” a reference to spiny members found in some genera.