Winterizing the Pistachio Tree

If you’re a fan of pistachios, you already know nothing can quite match a fresh batch, and it’s impossible to get any fresher than pistachios grown and picked by your own hand. Frequent readers of mine are undoubtedly familiar with my enthusiasm for the duchess of all nuts, the pistachio; that tiny, tasty luxury of the tongue bursting with unbeatable flavor. I can only hope I’ve inspired a few of you to save a space in your backyard for your very own pistachio paradise.  

However, those planning to grow should realize pistachio trees can be a picky bunch. To achieve growth potential, they require a certain climate which can be a bit tricky for the inexperienced to reproduce faithfully.

Achieving proper plant care during winter months frequently offers the greatest degree of struggle for pistachio growers new and experienced alike. Once they drop their leaves, pistachio trees require a period of cold-weather dormancy; spending around six weeks in temperatures between 15 and 45 °F is ideal for maximum harvest yield.

Exposure to prolonged bouts of winter cold below 15 °F or mild spells over 45 °F can damage or kill even the hardiest pistachio trees, which makes establishing a good grasp on winterization technique all the more essential for potential pistachio growers.  

Because pistachio leaves and flowers can be injured by early fall or late spring frosts, it is important to only attempt to plant if you live in (or can reproduce) a dry, arid region, where winter temperatures are cool but not overly frigid, and dramatic fluctuations in temperature are minimal. Almost all commercial growth of pistachios in the US takes place in western regions such as Arizona, New Mexico and California, so considering the climate patterns of those locations should provide an idea of the type of environment in which pistachios naturally thrive.

If you want to optimize spring growth, managing dead, snapped or entangled branches through a fall pruning will free up space for additional fruiting buds to develop. When pruning the branches of mature, dormant trees, try to leave around two or three vegetative buds in front of fruiting buds on each branch (vegetative buds are the smaller ones). To prevent disease, you should also remove any dead nuts still on the branch.

Other fall winterization techniques include insulating roots against cold-induced shock by applying a layer of mulch to the soil above the root system, and installing tree guards to keep animals from chewing away bark and roots. Many tree guards also reflect the sun, which prevents tree trunks from becoming overheated on sunny winter days.

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