Fall has officially commenced and leaves are starting to change colors in Iowa. The Iowa Department of Natural Resources says most trees are still green, however a few varieties are beginning to change including walnut, green ash, elm, and cottonwood showing some yellow. Some bright reds are also starting to make an appearance with sumac. Late summer rain will cause some trees to change early, mostly along the Mississippi River Valley. Central Iowa is seeing yellows arrive on elm, walnut, ash and cottonwood. And now shrubs and vines are changing too, with purple asters just beginning to flower in southern Iowa. The estimated peak time to see colorful treetops in southeastern Iowa will be October 20th.