The Weather and Fall Leaf Color
The following description appeared in the UT Agricultural Extension Service publication number SP 529 and was written by Dr. Wayne Clatterbuck, Assistant Professor of Forestry, Wildlife & Fisheries.
The amount, duration and brilliance of autumn color depend on weather conditions that occur before and during the time chlorophyll in the leaves is declining. Temperature, light and water supply are the primary factors that influence the synthesis of carbohydrates (sugars) that favors anthocyanin formation and bright fall color. Cool, but not freezing, temperatures favor anthocyanin production. Early frost is more likely to kill leaves, making them turn brown and fall sooner from the trees. Bright light favors red colors, so red color often develops on exposed leaves. Water supply also affects anthocyanin production, with mild drought favoring bright reds. Rainy days occurring near peak coloration will decrease color intensity. Late summer droughts can delay the onset of fall color by a few weeks. Temperature, sunlight and moisture are highly variable each year, assuring that no two autumns are alike.
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