‘Autumn leaves’: explained

Weather Blog

On average, Central Texas reaches peak fall foliage near the last week of November. This is when most trees display their most vibrant reds, oranges and yellows.

Why do leaves change colors?

In the spring and summer, chlorophyll (green pigment) inside leaves helps capture sunlight and create sugars the trees use as food (‘photosynthesis’). A thriving, healthy leaf exudes a dominant green hue, hiding the yellows/reds/oranges. In the fall, the food-making processes break down and chlorophyll is depleted, causing the green to disappear and the reds/yellows/oranges to become visible.

Facts about the changing of leaves:

  • Cold nights (>32°F) and bright sunshine help bring out more vibrant colors
  • Temperature, light and water supply all influence the intensity and duration of a tree’s fall colors
  • Leaves fall as a result of the tree cutting off it’s supply of nutrients and water to the leaves while simultaneously, building a layer of new cells at the stem of the leaf to protect the tree body — this causes the leaf to eventually weaken, die and fall
  • Decaying leaves at the base of the trees are a source of nutrients and water, helping to promote life in the next season
  • Some trees use the pigment as a type of sunscreen, filtering out sunshine (trees, can in fact, get “too much” sunlight)
  • Most conifers – pines, spruces, firs, hemlocks, cedars, etc. – are evergreen and keep their needle-like leaves year-round
  • Carotenes and xanthophyll pigments responsible for the orange/yellow color of leaves are what also give carrots their orange color

Fall foliage in 2019

According to KXAN’s First Warning Weather team, this season’s bright, fall colors could be a result of the early onset of cool temperatures. Many areas saw their first freezes of the season weeks ahead of schedule. In addition, a parade of cold fronts have kept most days cooler than normal for the majority of November.

More resources

— Click to see a photo gallery of last year’s fall foliage in Austin.
— Click here to see a map of peak fall foliage across the United States.
— Click here to see a variety of fall foliage webcams.

Copyright 2019 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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