John Burroughs, a well-known American naturalist and writer, once described October as "the time of the illuminated woods."

This is true in Minnesota, but we also need to add the month of September.

People from New York, New Hampshire and Maine believe that when the Northeast flares with its display of colorful leaves there is no other section of the country that compares with their autumn. I can understand their enthusiasm when they look out at the red maples, paper birches, tulip trees, sugar maples, red oaks and many other woody plants that add to the pageantry. Millions of people drive many miles on autumn weekends to see New England's concentrated palette of fall foliage.

That is great, but people in Minnesota and Wisconsin, China and Japan, Germany and Sweden, and other locations in the Northern Hemisphere can also enjoy the foliage color that often runs from September to November in their homelands.

The fall coloring is the result of chemical processes in the leaves as the seasons change, with many leaves turning before the first frost. Leaves stop their food-making process as temperatures drop and daylight diminishes. Chlorophyll in the leaves breaks down, the green color disappears, and the yellow pigment that was covered up becomes visible, giving the leaves part of their splendor. Other chemical changes occur and cause the formation of additional pigments that vary from yellow to red.

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.