Why Did My Chinese Pistache Lose All of Its Leaves Last Winter?
One of the few deciduous trees to display vibrant red autumn foliage color in the deserts of the American Southwest, the Chinese pistache (Pistacia chinensis) is also called the Chinese mastic or Chinese pistachio. Because of its multiple common names, it may be confused with other species of trees in the genus Pistacia, including a few that remain evergreen over the winter months. The Chinese pistache naturally loses its foliage in winter, regardless of its location where grow in U.S. Department of Agriculture plant hardiness zones 6b through 9. Does this Spark an idea?
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Natural Characteristics
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The Chinese pistache grows wild in the rather dry, rocky soils across central and southern China's warm temperate regions. It naturally looses its foliage every autumn as a means to conserve water and resources during the cool and/or dry months from fall to spring when growing isn't conducive. Even if the winter is frost-free and mild, Chinese pistache will still drop its foliage, albeit a bit later than in regions with chillier autumn weather.
Identity Confusion
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Because Chinese pistache is also called Chinese mastic, it may be easily confused with the evergreen tree known simply as mastic. Mastic is closely related to Chinese pistache, as they are both in the genus Pistacia. Mastic (Pistacia lentiscus) grows more slowly and matures slightly smaller than the Chinese pistache but remains evergreen over the winter and during summertime droughts. Mastic is one resilient evergreen tree for the hot, dry and nutrient-poor soils of the American Southwest. Moreover, the related trees Pistacia atlantica and Pistacia weinmanniifolia retain their foliage across winter, and may be thought to have been a Chinese pistache when purchased at the nursery or first identified in the landscape.
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Other Causes of Leaf Drop
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While you should expect your Chinese pistache tree to lose its leaves every winter the rest of its life, other conditions can lead to leaf drop and are of concern. This tree is resistant to oak root fungus but not verticillium wilt. Planting Chinese pistache in a wet or slow-draining soil causes stress and slowly suffocates the roots. Wet soils increases chances for fungal diseases which harms the tree, causing premature leaf drop in spring or summer. Fungus-infected trees may not survive the winter dormancy if soil drainage conditions do not improve.
Growth Tips
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Although extremely tolerant of drought and heat, Chinese pistache grows best if given some irrigation in summer to support more branch and leafy growth. However, the soil should always be well-drained. Full sun exposures result in a more uniform canopy and promotes better development of the orange to red foliage color in autumn. When the Chinese pistache is dormant and lacks leaves in winter, do not irrigate as wet soils in winter encourage fungal diseases during mild weather and heading into spring.
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References
- Learn2Grow: Pistacia Chinensis
- "Sunset Western Garden Book"; Kathleen Norris Brenzel, editor; 2007
- U.S. Forest Service; Pistacia Chinensis; Edward F. Gilman, et al.; Oct. 1994
- Flora of China; Pistacia; 2008
