Cacti in habitat

Cacti are a curious family. After centuries of familiarisation they no longer arouse the astonishment that they used to, either in Europe or other parts of the world. Nevertheless, they are surely no ordinary plants. They are so far removed from the 'common leafy plants' that their characteristic structure and particular development and extreme environment in which they are found have inspired many people to become lifelong collectors.

In their countries of origin, some cacti can live for hundreds of years. Following a long life in which they have conquered many dangers, the pillar-shaped giants of the family can reach heights of thirty to sixty feet. A large spherical barrel cactus can weigh a ton or more and evaporates several thousand times less water than an ordinary plant of the same weight. It is often said that cacti are experts in the art of survival, and this is very true. They grow in places where other plants would die. They have succeeded in adapting to extreme drought, and the capacity to form leaves eventually disappearing altogether. The function of the leaves were taken over by other parts of the plant. When there has been no rainfall for a long time, the cacti are in a sort of state of hibernation, reducing all the life processes to an absolute minimum. Some species even withdraw into the earth for protection, and apparently lifeless, wait for better times. When the rain comes at last, the delicate network of roots just below the surface acts like a huge sponge, in a short time soaking up every last drop of water. Cacti are like living reservoirs of water. The moisture is stored in the body of the plant and carefully protected against evaporation.

Many members of the cactus family have armed themselves against a hostile outside world with sharp spines, a dense cover of hair, or an armoured skin. Plants which can survive long, dry periods by storing water and using it very economically, are now run by the collective name, 'succulents', they tend to share a rather fleshy appearance.

The cactus family originates from America. Cacti which are apparently indigenous to the south of Europe, Africa, Australia or Asia have been introduced their by man for various reasons. In some cases the introduction of these spiny plant's had catastrophic results, as for example, in Australia, where huge areas of land are overrun with Opuntia.

The large cacti are often the most striking living organisms in the desert and semi- deserts because of their bizarre shapes and impressive size, and yet they are by no means alone. They live side by side with a large number of reptiles, insects, birds and mammals which have adapted to the climatological conditions, just like the cactus. No matter how effectively the cactus has armed itself with spines to protect its juicy body from being devoured and from other dangers, there are always some creatures which managed to break through the armour.

Like the cactus itself they have also learned to survive in arid regions. The gigantic columnar cactus (Carnegia gigantea) grows in the Sonora desert, a huge area which covers a large part of Mexico, as well as part of Arizona in the United States. In America this giant is known as 'saguaro'. When it is young, a small 'saguaro' is in grave danger from being devoured by hungry rodents, and even if it manages to reach the age of twenty five undamaged when the plant is still only twelve inches tall it is still at risk. Once the mature plant towers over the surrounding area the Hawk will build a nest in raised arms. The 'Gila woodpecker' can hammer around the spines with his long beak until they fall off, making a space where a whole can be picked out.