Pistachio Tree Climate Requirements
In a few words, pistachio tree thrives in areas with a long hot summer and a cold winter, as the tree must experience certain hours of cold that will break the buds dormancy. In United States, pistachios are commercially grown mostly in California (98% of production), but also in New Mexico, Arizona and Texas.
In general, the tree can tolerate very low air humidity and low soil moisture levels. On the contrary, high humidity levels negatively affect tree’s development. The pistachio tree thrives best in areas where winters are quite cold (in order to “break” the dormancy of the buds) and the summers are long, dry and hot with a temperature of 77-97 °F (25 to 35,5 °C), so that the fruit can mature. In hot and dry climate, (which is often found in areas close to the sea), pistachio tree performs well. In general, during the dormancy period of trees, low temperatures up to 14 °F (-10 °C) do not harm the trees. Pistachio trees can grow well in altitudes up to 2200 feet (670 meters), but in some cases they are grown even in altitudes up to 3300 (1000 meters).
Spring frosts during the flowering period generally do not damage the trees, due to late bloom. However, dry winds and cold wet weather during spring affect pollination and may reduce fruit set. Moreover, frequent rainfall and humid conditions during the summer (before or during the harvest period) can reduce fruit quality. Humid and hot weather during the growing season of trees also favor the development of fungal diseases. Therefore, pistachio trees can be grown commercially in hot and dry areas with cold winters, but preferably where irrigation is available.
Cold winters are necessary, as they satisfy the needs in cold of the female and male pistachio trees (on average 900 hours below 45 °F or 7 °C) and ensure timely and regular disruption of their dormancy. Moreover, cold winters promote the roughly simultaneous bloom of female and male pistachio trees and their normal vegetation. Lack of winter cold can create a major pollination problem. After a warm winter, due to incomplete interruption of dormancy, male trees bloom far earlier than the female trees. As a result, a great percentage of pollen is lost, something that results in decrease of fruit set and increase of empty nuts. Thus, the needs in cold of an average pistachio tree are satisfied by average winter temperatures of 45 °F or 7 °C (but not lower than 34 °F or 1 °C). If these temperatures are maintained for a month or so, then we will most possibly have a timely and regular interruption of buds dormancy.
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4.) Pistachio Tree Growing Conditions
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