Why Leaves Change Color?

Scientists don’t yet fully understand all of the complicated actions and interactions that produce the spectacular displays of autumn leaf colorsBiological illustration of a leaf's color change that are a highlight of the fall months. Although not fully understood, several factors affect when and how tree leaves change color and the hues they produce. These factors include:

 Why are fall trees more intense some years?

  1. Cool Night Temperatures – An extended period of cool night time temperatures below 45 degrees but above freezing helps to develop more anthocyanins in the leaves bringing out more intense fall colors in trees.
  2. Sunny Days – Bright sun filled days allow the leaves to trap the sugars from the dwindling chlorophyll creating fantastic fall color.
  3. Calm Days – Stormy and windy days help to release the leaves on the trees. An extended period of calm days help to enhance the viewing time of fall foliage.
  4. 2010 Fall Tree Prediction-See one experts guess on what to expect in 2010


James R. Fazio

James has a strong background and knowledge in forestry and tree care working in several forestry related jobs for the US Forest Service, Bureau of Land Management, Arbor Day Foundation, and as a Professor at the University of Idaho. One of his special areas of interest includes Urban and community forestry. Learn more about "Tree Care" at arborday.org

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