Answer: Fall leaf color change is more related to weather than to anything else. Sometimes the weather changes abruptly and leaves don't have enough time to react; sometimes the weather change is so gradual that trees miss the prompt. What your gingko needs is several weeks of warm days and crispy cold nights to signal it that it's time to change colors. I'll bet it will eventually figure out that it is supposed to change colors. Just be patient with it.
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