Areole

Areole is a term used in botany to describe a small, specialized growth point on the stem of a cactus. Areoles are a defining feature of cacti (family Cactaceae) and are the sites from which spines, branches, and flowers typically emerge. They are not found in most other plants, and they represent the plant’s basic unit of growth along the stem.

Structure and appearance can vary widely among species. Areoles are usually somewhat cushion-like or elongated bumps along the cactus ribs or stems and may be woolly or hairy. They frequently bear spines, but can also carry scales, hairs, or glochids in some genera. Each areole is a cluster of meristematic tissue that can give rise to new shoots or reproductive structures.

Function and development are straightforward: every areole is a potential point for growth and reproduction. Spines originate from areoles, serving as protection and shading, while flowers typically arise from areoles as well. In many cacti, a single areole can produce multiple flowers during a flowering period.

Variation among cacti is substantial. Some areoles are small and barely noticeable, while others form prominent, densely packed clusters. The presence, length, and arrangement of spines and the wool or scales on an areole help distinguish genera and species, making areoles useful in cactus identification and classification.