Autumn has fallen, as have many leaves on the trees as central Iowa nears the peak of foliage colors for the season.
The National Oceanic and Atmospheric Administration said on its website that a wet growing season followed by a dry autumn creates the most vibrant colors for fall. However, the drought conditions in the midwest this summer have caused many trees to trigger an early "shutdown" as they prepare for winter. This season, many leaves will fall from their trees before they reach their full color potential.
But, the early changing of the leaves offers more moderate weather for viewing fall colors. George Warford, of the State Forest Nursery, said in a report released on Oct. 1 that peak weekends for fall sightseeing will be Oct. 6 and 13. Warford said the golds from the green ash and hickory trees are vibrant and the reds from the red maple, sumac and burning bush are "spectacular." Bright yellows are also visible across the landscape. Oaks have yet to change yet, but are starting to show.
Tunnel Mill Park, south of Webster City, has changed color drastically since autumn began in late September. The State Forest Nursery said fall colors will be at their peak until Oct. 13.
The State Forest Nursery report indicates that much of Iowa will be experiencing similar peak dates, except for southern areas of the state. The peak in south central Iowa has already passed. Southwest Iowa will be hitting it's peak this weekend, rather than throughout next week.
The Iowa Department of Natural Resources said in a report about fall colors that the leaves change due to the winter dormancy in all perennial plants. A chemical called phytochrome triggers plants into their dormant period when nights become long enough. Trees then produce less and less chlorophyll, which manufactures carbohydrates for the plant and gives them a green color. This allows other pigments to show through the leaves. Food manufactured by the remaining chlorophyll builds up in the sap of the leaf, which causes the leaves to turn in color, depending on the acidity of the sap.
The IDNR report also discusses the different effects that weather has on trees. The dry weather of summer and fall causes a greater building up sugar, which enhances the redness of leaves.