Where Can You Grow Pistachio Trees?
Pistachios love the desert heat and are most often grown in New Mexico, Arizona and Southern California. They can grow in other dry, hot areas like West Texas as well, but do not do well in areas with cold winters or summers that stay under 100ºF for most of the season. America’s South Western deserts are both hot enough to supply this requirement and cool enough in the winters to allow the trees to go dormant.
Site Selection for Growing Pistachio Trees
Deep, sandy loam soils are best for pistachios, but they will do well in most desert soils. The poorer the soil, the closer the trees are planted together. Pistachios are tap root trees, so they need deep soil (7 or more feet).
They grow to 20-30 feet in height and about that in width in most cases. They require several deep irrigations during the winter, but are drought tolerant during the summer.
Planting Pistachio Trees
P. Vera is pollinated by wind, so the male and female trees need to be planted in specific patterns to take advantage of the breeze. The trees require between 12 and 20 feet of space, depending on the soil quality (closer together in poorer soils). Most nurseries sell rootstocks that are sold in biodegradable containers that can be planted with the tree. This is because handling or exposing the roots often has dire consequences for the tree. The hole should be just large enough to bury the planter completely.
Management and Pruning
After the rootstock trees are planted, they are usually grown to about 18 inches with all lateral shoots nipped. They are then left to spread as they wish. Established seedlings are then budded (grafted) in the fall, usually with a method called T-budding. Plenty of moisture the first year is needed for success and the budding process is usually done with harvested buds on the windward side. Once a tree framework has been established (the popular vase-shape in California is good for coastal areas, but deadly in the harsher deserts of Arizona and New Mexico), no other pruning is necessary other than to cut back sprawling branches.
Trees begin bearing fruit in the fourth or fifth year after budding, but don’t become fully productive until they are a decade or more in age. When the hulls separate easily from the shell, the nuts are ready. At this point, there are only 7-10 days of optimum harvest before staining will set in on the nuts as they over-ripen.
The trees are shaken and the nuts gathered from beneath. A large sheet under the tree works well to speed up that process. Nuts should be shelled or cured the same day to avoid staining. This requires drying to about 5% moisture. Be aware that when pistachio trees reach a ripe age (20 or more), they often go to biennial production with a heavy crop every other year and a light or empty crop in off years. This is normal.
Wilt in California is becoming more and more common in commercial orchards and, by extension, is moving into small backyard orchards as well. Called verticillium, there is no known fix for this, but the rootstock P. integerrima has been proven tolerant to the disease. Another process, called solarization, can be used to kill the verticillium, but it can be a hit-or-miss process.