Plants that grow in dry regions are known as xerophilous, a word which means they love dry places. The roots of these plants spread out horizontally close to the surface of the soil. In this way the roots can soak up whatever rain falls before the heat of the Sun evaporates all the moisture. Some times the roots of xerophilous plants go down deep into the soil to reach damper places or even a supply of water.

The stalks of xerophilous plants have no leaves and they are covered with a waxy material which prevents moisture from evaporating from the plant. These plants are also covered in sharp thorns or spines to stop animals from eating them.

In dry, desert areas these plants, and especially the cactil, are a precious source of water as well as food for living creatures. If they had no thorns to defend them they would all be eaten up by hungry and thirsty animals.

Many of these plants produce beautiful flowers and fruit after rain. The fruit can be eaten both by people and animals.