Deserts are defined not by heat, but by aridity. Most deserts have less than 10 inches of rainfall a year, and this is the natural situation in significant parts of the south-west of the United States. Climate change may be expected to extend the area subject to this regime. Although heat does not define desert areas, it is nonetheless true that many desert areas of the continental United States have average summer temperatures above 85?F.
For most of human history small numbers of passing nomads and smaller numbers of holy men and women seeking solitude were the only human inhabitants of deserts. Today, major water engineering projects like the Colorado River Basin Project permit the deserts to bloom with massive storage and reticulation infrastructure.
Your landscaping contractor will be sensitive not only to your needs as a client, but also to what eminent designer John Brookes has called the "visual vigor" of the desert landscape. Just as a good architect will conceive house plans that draw on the strengths of the desert, including the crystal quality of the light and the dry, invigorating air, so the landscape architect will draw of the strengths of the desertscape, rather than try to reproduce some northern or eastern suburban garden.
Natural desert planting has great visual strength. To reduce transpiration and conserve water, Nature has rolled out a whole bag of clever tricks: insulation is provided by hairy leaves and stems, leaves roll up tight in the heat - there are even some plants designed with no leaves at all - and waxy surfaces reduce water loss from leaves. Many desert plants are succulents, able to store water for themselves. These many strategies for desert living have produced considerable variety of plant form, well suited to the modernist designs favoured by many home owners for residences in these regions. Among the many species suited to desert growth are agaves, Artemisia, mesquite, ocotillo, prickly pear, tamarisk and Yucca.
The desert garden does not need to display only shades of silver-grey and green. Many species have cultivars that mean you can choose from a varied color range: agaves, golden barrel (Echinocactus grusonii), and some prickly pears (for example, Opuntia violacea santa-rita) can all introduce color notes to create a focal point in the garden. And then, of course, in due season the gardener can look forward to spectacular flower displays that erupt from long stems or directly from the plant surface.
Although water has been brought to the desert in abundance most gardeners, in these days of environmental awareness, will be careful not to waste this resource. In nature desert plantings are often sparse and well spread out: in the garden closer groupings of plants allows for more efficient use of water. Lawns may not be considered appropriate for desert environments, and the landscaper can create dramatic effects from alternative forms of surfacing, including scoria and many colors and textures of paving material.
Once inhospitable and forbidding, desert climates now create innovative, creative opportunities to create vibrant and beautiful gardens.