There's always a day when the fall colors hit their peak

I wrote in my journal on Oct. 14, 2014, that it was the overall fall color peak from the St. Cloud area south to Mankato and Northfield, including the Twin Cities. A glorious day with awesome beauty! It happened again on the same date last year.

There is a day each year when a certain area is truly at its best. To us, the special date is when the autumn foliage colors are spectacular considering the many trees, shrubs and vines that give us the fantastic show.

Some fall seasons are much more colorful than others because an early frost can kill the foliage, or a warm, cloudy autumn can produce dull colors. The striking color changes that take place, as deciduous woody plants prepare to drop their leaves, are triggered by shorter days and cooler weather.

As the seasons change from summer to winter, leaves stop their food-making processes and the making of chlorophyll ends. The green color fades and two underlying chemicals, carotene and xanthophylls, are unmasked, leaving yellow pigments. Red coloration appears only in those leaves that have certain sugars or tannins. Trapped in the leaf, they combine with other substances to produce a red pigment that colors the trees, shrubs and vines their glorious crimson. Within the same tree species, the degree of color may vary from tree to tree or branch to branch. Leaves exposed to the sunlight may turn red, while those on the shady side may be yellow. The foliage of some woody plants just turns dull brown from death and decay.

Jim Gilbert's Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays. He taught and worked as a naturalist for 50 years.