Double the fun and double the vegetables--that's what you get with vegetable gardening in the desert. Almost any vegetable will grow as long as there is sufficient water available and some protection from the sun during the hottest part of the day during the summer months. Vegetable gardening near Phoenix, Arizona was a practice of the Hohokam Indians when they inhabited the Valley of the Sun from 300 to 1400 CE.
Leafy greens such as spinach, kale, and chard--along with lettuces, cabbages, broccoli, and root vegetables like carrots, beets and turnips--are cool-season veggies. Plant them in the desert as soon as the last frost date in the spring and again about eight weeks before the first frost date in the fall. The days getting shorter as fall approaches means less bolting and cooler temperatures at night. Two crops are possible with cool-season veggies.
Warm Season Vegetables
Summers are long in most desert regions, beginning in late April and often lasting well into October with temperatures reaching a high of 90 degrees or more. It may seem counter-intuitive, but select vegetables that are early ripening. As temperatures go over 90 degrees in June and July without much moisture, pollen dries out before it can fertilize the blossoms of tomatoes, peppers, corn and eggplants. That means warm season veggies--such as those just mentioned and including squash, beans and melons--should be planted as soon as the soil warms up.
If daytime temperatures are in the 70s, the soil is most likely warm enough. Warm season veggies need warm soil to germinate and grow a healthy root system. If plants have made it through July, cut them back by at least half. They will put on a new flush of growth and it's often possible to get a second crop of warm-season vegetables.
Of course a water source is required for desert gardening. There isn't enough rainfall, even during monsoon season, to keep a vegetable garden alive. It may be necessary to water every other day during summer months. Quite a few veggies like eggplant and peppers will wilt even though the ground may be damp. That's okay, as the plants will revive in the evening and early morning hours.
Salts, Iron Deficiency and Fertilizing
Many desert areas have alkaline soil and the water is naturally salty. The salts build up in the soil and should be flushed out by watering deeply once a month. The soil is also deficient in iron. Plants show that deficiency by having green veins and yellow leaves. Nitrogen deficiency is shown by the leaves turning entirely yellow. Adding iron to amend the soil solves the problem.
Fertilizing in the desert should be done more often, since the extra watering dissolves the fertilizer and it washes away. Use a water-soluble fertilizer every two weeks for more productive crops.
During the summer months most veggies appreciate protection from the hot sun. If possible locate the garden where it receives eight hours of direct sunlight in the morning and shade in the afternoon.