Saturday, November 10, 2018

Fall changes

This time of year the Hudson Valley is famous for its fall foliage displays. Reds, yellows, oranges and browns catch the sunlight and fall to the ground just before snow comes. But what is actually happening when leaves change colors? During spring and summer, green leaves get their color from food-making chlorophyll. The chemical absorbs sunlight, turning carbon dioxide and water into carbohydrates that sustain the trees. The leaves contain other pigments like yellow and red but these are masked by more prevalent green. Fall brings cooler temperatures and less sunlight which trigger trees to stop making food. Chlorophyll breaks down and disappears, leaving yellows, oranges, and reds.

What affects leaf changes? Mild autumn temperatures, not warm or freezing, are ideal. Severe drought can cause leaves to drop early, and violent winds rip leaves from trees prematurely

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