Different types of cacti plants in pots.

What You Need to Know About the Cacti Plants

The cactus family have adapted to the con­ditions in which they grow by reducing their surface area to a moisture-conserving minimum. They are all succulents in that they store moisture within the main part of the plant itself, but the two types of cactus — desert and rain forest — have differing adaptations.

To cope with hot weather and long periods of drought, desert- type cacti have a waxy outer covering (cuticle) and ridges on their stems, and their leaves have become spines or hairs. These spines grow from cushion­ shaped, modified side shoots (areoles), sometimes on wart-like swellings (tubercles). The areoles are the points at which flowers and offsets arise.

Rain-forest cacti establish in places where debris has accumulated, such as on tree branches. Despite the generally humid rain forest atmosphere, these pockets dry out quickly, so moisture needs to be stored within the plant. They do not grow in the upright, cylindrical shape common to many desert cacti, but tend to have long, trailing, modified stems consisting of numerous, leaf like segments.