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Article #39, September 2000
By Bill Cook

   It seems to me that Fall has crept up on me.  Itís here and Iím having a hard time figuring out how I can have so many summer things left undone.  Itís time to change gears and ready for the grand Autumn season. 

   The usual vanguard of stressed trees have changed color first.  Red maples in the swamp have gone scarlet.  Aspens, black ash, sugar maple, and other species that logged a poor season are checking out early.  But the bulk of the trees will turn during the end of September and into October.  The leaf-peeper season.

   Despite the fairly good growing season and the increased frequency of frost activity, the internal clock that trees use to change colors has little to do with weather.  Itís the photoperiod.  The relative number of hours of light and dark in a day.  Now, some tree species are more, or less, opportunistic.  Not all trees operate on the same clock.  But in general, itís the photoperiod that affects the timing of leaf drop, not nut crops, or woolly bears, or bird migrations.

   This year, many trees were forced into producing a second set of leaves.  A variety of insects munched the first tender crop into non-existence by the end of June.  Cankerworms, leaf-rollers, casebearers, and forest tent caterpillars caused significant defoliation of aspen, maple, and many other species.  While these are all normal occurrences in the life of a forest, the stress may contribute to an earlier Fall color change in some parts of the Upper Peninsula.   But itís dangerous to predict color change patterns. 

   While timing is largely controlled by photoperiod, the intensity and visual quality of the Fall colors can be impacted by weather.  Stress might precipitate a more effective or quicker re-absorption of the green chlorophyll pigments.  The red, yellow, and purple pigments may stand out better, maybe for a little longer.  Frost can also have influence on the quality of Fall colors. 

  The biggest portion of our hardwood, or broad-leaf, forests consist of maples, aspens, and birches.  The crimson and gold of maples we all know about, which pretty much knocks the socks off color changes in other parts of the country.  Our aspens also turn a fantastic yellow color, with the right weather conditions.  Birch are much the same way.  A bright yellow pure paper birch stand, with snow-white bark, is an experience not soon forgotten. 

   But, let us not forget the softwoods, or evergreens.  Although they do retain needles year-round, they donít retain them all.  The older needles, nearer to the trunk, fall off every year.  The only exception to this is the glorious tamarack.  Not only does it lose all its needles each Fall, but it departs the season in a blaze of gold! 

   Each season hosts a multitude of changes in the forest and with the wildlife that live there.  The Fall color change may be the most hailed of all seasonal changes, but the outdoors is full of fascinating and interesting events this time of the year.  What new things might you discover hidden amid the kaleidoscope of Fall?

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Bill Cook is an MSU Extension forester providing educational programming for the entire Upper Peninsula. His office is located at the MSU Upper Peninsula Tree Improvement Center near Escanaba. The Center is the headquarters for three MSU Forestry properties in the U.P., with a combined area of about 8,000 acres. He can be reached at cookwi@msu.edu or 906-786-1575.

Prepared by Bill Cook, Forester/Biologist, Michigan State University Extension, 6005 J Road, Escanaba, MI  49829
906-786-1575 (voice),  906-786-9370 (fax),  e-mail:  cookwi@msu.edu

Use / reprinting of these articles is encouraged. Please notify Bill Cook.
By-line should read "Bill Cook, MSU Extension" Please use the article trailer whenever possible.

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