Ask the Master Gardener

Trees changing color early? Stress is likely reason

By: Laurie Meyerpeter, Placer County Master Gardener
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Question: I have a number of Chinese Pistache trees lining my driveway and this fall, one tree turned color much, much earlier than the others. Why?

Answer: A number of factors cause trees to turn color in the fall. The shortening days are the primary influence followed by the particular characteristics of different types of trees. Cool nights and warmer afternoons heighten and accentuate fall color but is a secondary influence.

Since your trees are all Chinese Pistache trees, they should change color at a roughly similar time. There may be some slight variability since most Chinese Pistache trees are grown from seed and different trees do vary some. (There is a variety called “Keith Davy” that is grown from budding onto seedling stock. This cultivar has uniform orange-red color in the fall, good form and no fruit.)

However, since there is such a dramatic variance in the time frame of color change, it is likely the tree in question is experiencing more stress than the other trees.

Check irrigation and watering practices for that particular tree. If it is watered with drip irrigation, it is possible that the emitters are clogged or not flowing as freely on that tree. If the tree is watered with other forms of irrigation, there might have been more run-off where the particular tree is growing that prevented water from soaking deeply into the ground in that area.

A lack of sufficient water is a frequent cause of premature color change, which may have been compounded with our very hot summer.

Other possible causes of stress to check for are weed eater damage at the base, rodent damage, herbicide damage, root damage due to a construction o

landscape project near the root zone, or other factors that can stress the tree.
Stress that is severe enough to cause premature fall color can be harmful to the tree so it is a good idea to search for a cause and to prevent this occurrence next year.

Have gardening questions? Call the Master Gardener hotline at (530) 889-7388.