Because many areas of the Southwest could be classified as arid regions, gardeners must have an understanding of the water requirements of each of the plants they put into the ground. Rainfall is not plentiful enough, or reliable enough, to contribute sufficient water to support plant growth. In the warm deserts of the Southwest, gardeners have the excitement of being able to grow vegetables both in the spring/summer period and then another crop in the fall and winter. Nearly every variety of vegetable can be grown in the Southwest.
Plan the garden, taking the seasons into account. Elevation is a primary determinant of climate and therefore the timing and length of the growing season. In the lower, warmer desert elevations, gardeners begin planting in February as soon as danger of frost has passed.
In higher elevations, the growing season for vegetables does not begin until April or May---similar to that of the Midwest. Desert gardening has a unique schedule. Vegetables such as lettuce and spinach that prefer cooler temperatures must be planted early enough so they produce before the tremendous heat sets in at the beginning of summer. Spring summer crops that work well include bell peppers, corn, squash, tomatoes, watermelons and cantaloupe. Crops that work well in the fall/winter season include root vegetables, leafy greens, peas and beans.
Prepare the soil. Southwestern soils are usually not ideal for growing vegetables, which means they must be amended with compost that has nutrients to encourage plant growth. Dig down a foot and a half, taking out enough soil to make a 50/50 mix of original soil and compost. Top the bed with additional compost and let it sit for a week or more. It may take several growing seasons of mixing in additional compost before the soil is of the quality that is best for growing vegetables. The soil must be deeply turned to mix the amendments in properly. In many areas, you must remove rocks from the soil as well.
Install a watering system. The hot dry weather frequently seen in the Southwest can cause a lot of stress for vegetables. Care must be taken to supply the water they need to survive and produce fruit---but not over water them either, which can lead to a condition called root rot. Sprinklers that spray water high in the air are not a good solution because they do not water evenly and water can be lost to evaporation. Drip irrigation systems with plastic emitters are recommended. Different emitters can be used for each plant depending on their needs. Plastic tubing with a sequence of holes, called soaker hoses, are also a valuable tool for gardeners.
Avoid summer stress. Vegetables we associate with summer such as squash and tomatoes grow well in the Southwest, but may need help to survive the brutal heat of June through August. Put grass clippings, straw or other mulch material over the vegetable bed to help keep moisture in the soil. You can also place your vegetable bed in a location that receives shade from the afternoon sun, such as the eastern side of a fence. Some gardeners place white sheets over plants during the heat of the day. You can also build a shade system, a framework to place over the garden and cover with a dark shade cloth.