Anyone observing the severe, arid conditions of the desert must be amazed that there is any plant life there at all. You may wonder how the plants have adapted to the circumstances of their location.
Notice that desert plants do not have leaves, or the few plants which do have leaves, such as the creosote bush or ocotillo, grow very small ones which drop off in early summer. The cacti you see commonly in the desert have spines rather than leaves. These spines contain no openings, so they do not lose moisture once they take it in. They also serve to trap a layer of air as insulation for the plant. Beyond these benefits, the spines serve to discourage any animal from grazing on the plant. There is also a natural sap produced by the cacti that serves to keep them moist when there is no rain. If the cactus or other succulent plant is cut or bruised, this gummy sap dries and serves as a kind of bandage to keep the plant from losing its inner moisture. A waxy coating further protects the cactus from water loss.
There are some desert plants, such as the jade, which feature a kind of leaves that draw gases from the air at night. The leaf openings then close during the day to prevent any water loss.
The spacing of desert plants can educate us on how some of them survive in these harsh conditions. They not only need the ability to hold their limited moisture; some of them effectively compete for space. The creosote bush not only sheds its leaves and twigs readily in drought conditions, but secretes a toxic substance from its roots to kill the seedlings of any other plants trying to grow nearby. They often appear quite evenly spaced, as though purposely planted by someone, the spacing depending on how much rain they’ve received. If there are heavy rains, the moisture will drive the root poison deeper into the soil. This causes the creosote bushes to grow closer together.
Another desert plant, the Australian saltbush, appears gray due to an actual protective coating of salt. It is deep-rooted and therefore can survive temperatures well below freezing as well as withstanding the harsh sun.
If there are spring rains in the desert, the ocotillo, normally a thorny long-branched brown specimen, will grow small green leaves and bright red flowers at the tips. The leaves do remain small to minimize moisture loss. However, the spring awakening rarely lasts long. By the beginning of the summer season, the ocotillo will shed its leaves and flowers and go right back to the utility of its former long, brown appearance.
You can make a small cactus garden of your own as a microcosm of desert circumstances. It’s best to use a shallow clay container and sandy soil. Remember to give your cacti lots of sun but little water!