Grapefruit is a warm weather fruit so the climate in Arizona suits it just fine. What Arizona lacks, and the grapefruit demands, is 36 to 44 inches of rain, evenly distributed throughout the year. As well, soils in Arizona gardens tend to be salty so you will need extra water to keep the salt at bay. If you are planning on growing grapefruit, choose the right rootstock for your soil pH and type.
Plant your grapefruit tree in an area that gets all-day sun.
Build a watering basin around the tree. To do this, mound the soil 3 inches high and 8 inches wide. Form the soil into a ring, around the tree, 8 inches from the trunk.
Throw a 3-inch layer of mulch in the watering basin and spread it evenly around the tree. Keep the mulch at least 4 inches from the trunk of the tree.
Allow the soil to dry out between waterings. In the summer, water every week and in the winter cut back to watering once every four weeks. When you do water, flood the tree, allowing the water basin to fill and drain. Repeat this procedure for 30 minutes to one hour.
Inspect the grapefruit tree periodically for signs of disease. Psorosis is common on Arizona grapefruit trees and can be recognized by elongated patches on young leaves. If you are unsure if the tree is diseased, take a leaf sample to your county cooperative extension agent. She should be able to provide a diagnosis and suggestions on how to treat the tree.