Only specialized plants can survive the climate of a desert because deserts are regions with very little rainfall. The entire yearly rainfall occurs during a few days or weeks in spring. For the remaining ten or eleven months of the year, desert plants must survive without rain. There are two types of desert plants: annuals and perennials. Desert annuals, such as grasses and flowers, survive from one year to the next by existing through the long, hot, dry season in the form of seeds. These seeds remain inactive if the right amount of rain does not fall. If there isn’t enough rain, they wait until the following year or even the next. Another factor that helps these plants to survive is the fact that their life cycles are short. If they get the right amount of rainfall, the seeds grow into plants which flower, then form new seeds and finally die, all in just a few days or weeks. By the time the water from the spring rains disappears – just a few weeks after it falls – the desert annuals don’t need any.
Desert perennials also have special characteristics which enable them to survive as plants for several years. Nearly all perennials have a well-developed root system below ground (which enables the plant to absorb the maximum amount of water possible in a short time) and a comparatively small shoot system, that is, leaves and branches (which limits water loss). Another characteristic of many desert perennials is their deciduous habit; that is, after the rainy season they lose their leaves to prepare for the long, dry season, just as trees in wetter climates lose theirs to prepare for the winter. This reduces their water loss during the dry season to a minimum. Then, in the next rainy season they come fully alive once more, and grow new branches, leaves and flowers, just as the desert annuals do.