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A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

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Saturday - October 20, 2012

From: Stockton, CA
Region: California
Topic: Non-Natives, Diseases and Disorders, Pests, Edible Plants, Trees
Title: Spots on non-native naval orange trees from Stockton CA
Answered by: Barbara Medford


I have two mature Navel Orange trees. One tree has developed spotty chlorophyl depleted areas that were not on the oranges when they were smaller. In addition, the oranges on both trees are smaller , by half, than normal for this time of year. Tanglo and Lemon on both sides show no sign of this problem..It really looks like something is eating small areas of chlorophyl.


Citrus x sinensis means it's not from around here, not even in California. Orange trees probably originated in Southeast Asia and were cultivated in China by 2500 BC. We always want to know where a plant is native, because that helps us know in what soils, rainfall and climate it grows well. The Lady Bird Johnson Wildflower Center, home of Mr. Smarty Plants, is dedicated to the growth, protection and propagation of plants native not only to North America but to areas where those plants grow naturally.

Even though we will have no information in our Native Plant Database on oranges, we will try to find some websites that might give you some clues:

University of Florida Extension Citrus Black Spot Symptoms in Brazil.

San Francisco Chronicle Citrus Fruit with Black Spots

To get information on a plant that is not necessarily native but does grow locally, we suggest you contact the University of California Cooperative Extension Office in San Joaquin County.



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