cactus

Cactus refers to members of the plant family Cactaceae, a diverse group of flowering plants native to the Americas. Cacti are adapted to arid and semiarid environments and are found from Patagonia to western Canada, with the greatest diversity in deserts of Mexico and South America. They are characterized by thick, fleshy stems that store water, spines derived from specialized structures called areoles, and sparse or absent leaves. Many species use Crassulacean acid metabolism (CAM) to fix carbon at night, reducing water loss.

Morphology and adaptations: The stem is typically the photosynthetic organ, often ribbed or ridged to allow expansion after rain. Spines provide shade, reduce airflow close to the surface, and deter herbivores. Roots are usually wide-spread and shallow, enabling quick uptake of surface moisture, though some species have deep taproots. Areoles, not nodes or buds, are unique to cacti and give rise to spines, branches, and flowers.

Reproduction and ecology: Cacti produce large, often conspicuous flowers from areoles. Flowers may bloom for a short period and can be pollinated by bees, birds, or bats, depending on the species. Fruits are frequently fleshy and edible, containing seeds that disperse in various ways. Cacti occupy a range of habitats, including deserts, scrublands, and high-elevation regions, and are well adapted to drought and poor soils.

Human uses and conservation: Many cacti are cultivated as ornamentals in homes and landscapes. Some species, such as prickly pear (Opuntia) and saguaro (Carnegiea gigantea), have cultural or economic importance for edible fruits or other products. Some species are threatened by habitat loss, overcollection, or climate change; others have become invasive outside their native range.