cactoid

Cactoid is a botanical term used to describe plants or plant forms that resemble cacti in habit and appearance, though not necessarily belonging to the cactus family. As an adjective, it denotes cactus-like morphology, especially features such as a thick, succulent stem, vertical or angular ribs, and the presence of spines or spines-like projections. The term can also function as a noun, referring to an organism with a cactoid form.

True cacti belong to the family Cactaceae and are characterized by areoles, specialized structures from which spines, flowers, and new shoots arise. By contrast, cactoid plants may mimic some cactus traits without having areoles, and they may belong to other plant families, such as Euphorbiaceae or Asclepiadaceae. The resemblance is an example of convergent evolution driven by similar environmental pressures in arid regions.

In horticulture and botany, cactoid descriptions are primarily used descriptively in cataloging and garden design. The term emphasizes morphology rather than taxonomic relatedness, and it highlights the variety of adaptations that can imitate cacti.

Related topics include cactus, succulent plants, spines, areoles, and plant adaptations to arid environments.