Cactoideae

Cactoideae is the largest subfamily of the cactus family, Cactaceae, comprising the majority of cactus species and genera. The group is native almost entirely to the Americas, with the greatest diversity in Mexico and in many Andean and South American regions. Members occupy a wide range of arid and semi-arid habitats, from deserts to highland scrub and savannas.

Morphology and anatomy: Cactoideae species are characterized by succulent, photosynthetic stems carrying areoles with spines. Leaves are reduced to ephemeral structures or are absent. Stems vary in form, often ribbed or tuberculate, and may be globose, cylindrical, or columnar. Flowers are typically large relative to stem size, often funnel- or cup-shaped, with numerous petals and a central cluster of stamens. Fruits range from dry to fleshy and may contain many small seeds.

Taxonomy and diversity: Cactoideae comprises numerous genera organized into multiple tribes, with molecular phylogenetic studies refining their circumscription and relationships. It includes many species frequently encountered in cultivation, such as Mammillaria, Ferocactus, Echinocactus, Echinopsis, Gymnocalycium, and Carnegiea, among others.

Ecology and use: Cacti of this subfamily display a variety of growth forms, from small cushions to tall columnar giants. They are important nectar sources for pollinators and are widely cultivated as ornamentals for their diverse shapes and flowers. Conservation concerns for some species arise from habitat loss and collecting pressure.