In many ways, olives (Olea europaea) and citrus trees (Citrus spp.) prefer similar growing conditions and are often grown in the same regions. They can both be grown in U.S. Department of Agriculture plant hardiness zones 9 through 11, though olives are slightly more cold-hardy than most species of citrus. The main difference in climatic preferences between the two is that olives are of Mediterranean origin and thrive in arid climates, while citrus are subtropical fruits that require more moisture.
Olives grow in most regions of California. The hot, dry summers and mild winters are perfect for olives, as well as citrus. Almost every variety of citrus imaginable can be grown in California, though the trees require large quantities of water in summer. Though watering needs are high for California citrus, the dry air is of great benefit in preventing diseases because the many fungal diseases that attack citrus thrive in moist conditions. Note that olives are considered invasive in some areas, so check before planting.
The growing range of olives and citrus extend into low elevation areas of Arizona, New Mexico, and western Texas, wherever winter temperatures stay above 20 degrees Fahrenheit. Commercial production in these areas is not as widespread, but citrus and olive trees are common in home gardens. Most of the southern half of Arizona is suitable for citrus and olives. In New Mexico, only small pockets of low elevation desert in the southwest corner of the state are suitable and only the Rio Grande river valley in west Texas is reliably warm enough to prevent winter damage to the trees.
Most citrus grow in Florida's moist, subtropical climate. Olives also grow in Florida, though the high humidity limits their success as a commercial crop. "Arbequina," "Mission" and "Pendolino" are three olive varieties that thrive in Florida's wet climate. Olives appreciate the sandy soils in Florida and are tolerant of salty coastal conditions, often growing within a stone's throw of the ocean.
The growing range of citrus and olives extends all along the coastal areas of the south, from South Carolina to the Gulf Coast of Texas. In South Carolina, Georgia, Alabama and Mississippi, citrus and olives grow in only a narrow band along the coast. Most of southern Louisiana and southeastern Texas along the Gulf Coast is warm enough to support many types of citrus. Olives, though they can be grown here, are not common due to the humidity.
Growing With Winter Protection
Many dwarf citrus will grow in containers, which means you can bring them indoors for the winter in cooler climates. Similarly, olives can be pruned severely and successfully grown as a bush form in containers. If you live in USDA zone 8, you may be able to grow olives and some citrus outside if you provide protection or heating on the coldest nights.