Vegetable gardening in Arizona will differ depending on where in the state you are located. The Arizona Master Gardener's Manual advises that home soil test kits prove inadequate for accurate testing of Arizona soils, and that soil should be sent to laboratories for proper testing. Since Arizona contains elevations ranging from nearly sea level to above 7,000 feet, more specific instructions can be found by contacting your county's cooperative extension office. Plant according to climate and season no matter where in Arizona you are located.
Plan your garden. For a continuous harvest, consider interplanting or succession planting. Interplanting considers the growth cycles of two or more types of plants, as well as their nutritional needs and suitability as garden companions. Succession planting involves timing and continually starting new crops indoors so that they are ready to transplant outdoors when prior crops are no longer producing. Both methods ensure continual harvesting all season long.
Consider the season when you will be starting your garden. Peas, lettuces, kale and members of the cabbage family are all vegetables that do well in cool seasons. Some of these vegetables are even slightly frost-hardy. Garlic requires overwintering in the ground outside to reach peak performance the following spring. Tomatoes, peppers and cucumbers all require a hot season to do well. If it is too hot, however, they will cease to produce. If you live in Southern Arizona, planting cool-season vegetables in late summer will give you a wonderful fall vegetable bounty.
Start vegetables that require a long growing season indoors. Tomatoes and peppers will both do better when started this way. Choose a sunny window, preferably south-facing. Sow seeds in starter mix in a flat according to package instructions. Apply fertilizer once seeds have shown their first true (not seed case) leaves. Transplant outdoors after weather has warmed in your part of Arizona and temperature is consistently above 50 degrees Fahrenheit.
Sow cool-season vegetables directly in the soil, as most do not transplant very well. These include lettuces, peas, kale and members of the onion family. Dig compost into the planting site to help add nutrients to the soil and improve its friability.
Use trellises to increase your available space by growing vertically. Tomatoes, beans, peas and cucumbers all benefit from being grown on trellises. Cut some used pantyhose into strips to form strong ties that will not bruise or cut sensitive vegetable vines.
Water and fertilize regularly. Arizona soils are commonly lacking in nitrogen and phosphate, so make sure to apply fertilizers that boost these nutrients. Pay special attention to your plants on days that are very hot. Water in the evening on those days, so that the water droplets do not cause the plants to get sun scald when in direct midday sun.