Monday, September 21, 2009

Fall Color Prediction

Nature Watch
By Susan Benson,
CNHM Director of Education

What will the fall colors be like this month and next? I was contacted this week by Midwest Weekends travel guide to predict the fall colors for the Cable area. I felt a little nervous about making such a bold statement. My biggest fear was, “What if I’m wrong?” I decided to go out on a limb (yes, pun intended,) and make my prediction. It then became obvious around the Museum office that it had to be shared with the Nature Watch audience. So, will the colors be good this fall? Here is my prediction…

I predict that we could have a great fall color experience, and this is why. Here are the fall color basics. Three types of pigments are involved in autumn color. The first is chlorophyll, which gives leaves their basic green color. Chlorophyll is necessary for photosynthesis, the chemical reaction in which plants use the energy of sunlight to make sugars. The second pigment group, called carotenoids, produces yellow, orange, and brown colors. The last essential pigment, known as anthocyanin, produces red, purple, and crimson colors.

Both chlorophyll and carotenoids are present in leaves throughout the growing season. Most anthocyanins are produced only in autumn, in response to bright light and excess plant sugars within leaf cells. As the nights grow longer, chlorophyll production slows to a halt. Its green color fades from the leaves; the caroteniods and anthocyanins are then unmasked to show their colors.

The vibrancy of the colors is related to weather conditions that occur before and during the time when the chlorophyll in the leaves is dwindling. The series of warm, sunny days and cool, crisp but not freezing nights we have been experiencing seems to bring about the most spectacular color displays. During these days, a lot of sugars are produced. The cool nights and the gradual closing of veins leading from the leaf prevent these sugars from moving out. Lots of sugar and lots of light spur the production of the brilliant anthocyanin pigments.

The timing of the color change also varies by species. For example, oaks show their colors long after other species have already dropped their leaves. The differences in timing among species seems to be genetic, for a particular species at the same latitude will show the same coloration in high elevations at about the same time as it does in warmer lowlands.

Here is the unknown wild card. The amount of moisture in the soils also affects autumn colors. A late spring, or severe summer drought, which we have had, can delay the onset of fall color by a few weeks. They can also lower the intensity.

Perhaps it is only the optimist in me that thinks that the colors will be great, but regardless, we should all enjoy the experience. This is the best time of year to get outdoors, now that the insects are declining, and the trees colors greet us every where we go. Take a fall color tour. Attend the fall fest activities in many of our local communities. Go for a trek on one of our numerous hiking or biking trails. I hope to see you on the trail!

For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and exhibits, the Curiosity Center and Brain Teasers 2, in Cable at 13470 County Highway M. Also find us on the web at to learn more about exhibits and programs.

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