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Fall Leaves: Part 1

This week, with fall foliage at its peak here in Maine, I plan to focus a few posts on leaves. The subject is on everyone’s mind, as witnessed by this segment we produced with Good Morning America last Friday: abcnews.go.com/video/playerIndex?id=8789909.

Our posts will focus on collection techniques, as well as how to compost leaves and how to use them as fertilizer. But first, here is some background on why leaves fall to the ground in the first place:

1) As the day length shortens during September and October, chlorophyll production in the leaves of deciduous trees slows and then ceases. As chlorophyll is used up, the green subsides and other leaf colors are revealed. The colors were present all along, but the green masked the reds, oranges and yellows.
2) Why does chlorophyll production stop? Scientists say this is the trees’ natural response to diminishing supplies of water as we head toward winter. The tree instinctively knows that the ground will soon freeze and it won’t have enough water to conduct normal summer processes, so it sheds leaves as a protective mechanism.
3) Once the tree or shrub stops making chlorophyll, temperature and the amount of sunshine determines how fast the chlorophyll breaks down. Bright, sunny days and cool nights make chlorophyll break down more quickly in most trees, which makes the leaf colors especially bright. Extended cloudy or warm periods allow the chlorophyll to remain in the leaves longer, making colors more muted. If chlorophyll breaks down really slowly, leaves simply die and turn brown — which is often what happens in more southerly climates.
4) Especially dry summers can also mute autumn colors, and early autumn freezes can knock off many leaves before they turn colors.
5) You should know that every tree is different, depending on its genetic makeup. Researchers at the Royal Institute of Technology in Stockholm, Sweden, have reportedly mapped the “genetic timetable” of a tree in DNA, which may be useful in future breeding efforts for plants with exceptional fall color.

After reading all of this, you just want to know whether leaf-peeping will be good or bad this year. Right? Based on the factors listed above, my guess is that fall color will be above average in the North, with a long foliage season that has already begun along some roadsides, and certainly in more northern areas of our region. It’s been moist throughout the summer.

Here’s one thing you can do to help: If you have a favored sugar maple in the front yard, make sure it has plenty of water throughout September and October each year. That will help the plant hold its leaves longer in the fall, and generally make the plant healthier as it heads into winter

About The Author

Paul Tukey

An international leader of the green movement, Mr. Tukey is a journalist, author, filmmaker, TV host, activist and award-winning public speaker, who is widely recognized as North America's leading advocate for landscape sustainability and toxic pesticide reduction strategies.

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