Submitted to the Contra Costa Times on January 7, 2005

Q. How difficult is it to grow Pistachio trees?

A. Pistachio trees have been grown by humans for a very long time, perhaps as long as 9000 years. It is one of the oldest tree crops known. Originally from Asia Minor, the trees were brought into Syria and from there spread around the Mediterranean countries. The trees do well in much of California, and have become an important crop in the state.

Pistachio trees do best in areas with dry, warm summers and cool winters. Depending on the cultivar, they need between 600 and 1500 chill hours in the winter months. ‘Chill hours’ refers to hours where the temperature is below 45F. If you live next to the bay, you may not have enough chill hours for the flowers buds to break dormancy. Pistachio trees are large and wide, capable of slowly reaching 30’ with multiple trunks. You will need to have space for two trees as they are dioecious, with male and female blossoms on different trees. If you want fruit, you will need one of each, or graft a branch of a male tree onto the female. Pistachio trees are graceful ornamentals, with a slightly weeping habit and good foliage, and very long-lived if the conditions are good. Ideally, they should be planted in deep, friable soil in full sun with excellent drainage. They will survive in less perfect conditions, but must have good drainage. The trees are not happy in lawns, preferring deep infrequent watering. In wet soils the trees become susceptible to Verticillium wilt fungus and Armillaria mellea or Oak Root fungus. The trees are usually grafted onto resistant root stock, but incorrect watering can overwhelm them regardless.

It can take up to 7 years for a tree to begin bearing, but will not reach full production until they are 12-13 years old.. Fully mature trees will produce about 50 pounds of nuts every other season.

There are several publications you may want to look at. California Rare Fruit Growers have information on their web-site: http://www.crfg.org/pubs/ff/pistachio.html; Paul Vossen, the farm advisor for Sonoma and Marin has a pdf document that describes the various rootstocks and varietal differences at http://homeorchard.ucdavis.edu/Pistachio.shtml; and the University of California Cooperative Extension has a down-loadable document on the costs of establishing and producing Pistachios at http://fruitsandnuts.ucdavis.edu/crops/pistachio.shtml . It is also available from the UCCE Contra Costa office.