A wide array of fall colors were on display the past few weeks as trees changed colors and continue to drop leaves. Carl Hoffman, Stearns County Extension horticulturist, explained why leaves change colors in the fall. Hoffman said that leaves have two pigments-chlorophyll, which is the green color seen most of the year, and carotenes, which are pigments in the leaves, yellow or orange. According to Iowa’s DNR Web site, www.iowadnr.com/forestry/fallcolor, chlorophyll produces carbohydrates (sugars) which are used as food. In the summer, trees actively grow and feed. Chlorophyll is at a higher level and is constantly replaced. This makes leaves appear green. Hoffman said, “The green masks the other pigments.” As evening temperatures dropped in fall, the cooler nights destroy the plants chlorophyll, which releases the carotenes. This results in a color change. Carotenes (pigments) can be displayed at original color or mixed with the chlorophyll. “The sugars (chlorophyll) combine with yellow and orange pigments to make red or purple pigments,” Hoffman said. “If we have a relatively dry fall, warm days and color nights, we are going to see more colors, Hoffman said. Ideal conditions appeared in Wisconsin this year. As a result, the state had which more colors in their leaves. “Wisconsin’s color was gorgeous this year,” Hoffman said, after just returning from a trip where he drove through the neighboring state. Conversely, if there is a lot of moisture in fall, the color won’t be as good. “The color [in Minnesota] wasn’t as good this year, not like we have seen many other years,” Hoffman said. The longevity of colors depend on abscission or the process where leaves separated from stems. Hoffman said that this year’s summer drought caused the process to happen sooner. He said that when trees are not getting enough water, they have earlier abscission. The trees use this process as a defense mechanism during droughts to cut off the leaves’ water supply. The color life span is also affected by the amount and strength of wind. Warm days and cool nights resulted in earlier change colors. Likewise, early abscission and wind caused trees to lose their leaves. But it is not too late to enjoy the fall colors. Leaves can still be seen around the Kimball area, downtown and in rural, wooded areas. More information on fall leaves is available on the science educators Web site ncnatural.com/wildflwr/fall/science.
