Green ashes exhibiting perfect fall color. Photo taken September 2009 in Clayton,Wis

A resent argument that came up persuaded me to make a post discussing the different between fall color and pre mature color of leaves caused by stress or disease. This information which could prove to be helpful to area residents. First it is a good idea to know what causes leave to turn in fall. Many know that the chlorophyll reducing and the colors of the leaves appearing are the initial way colors show up in leaves, the effect is caused by the shortening days and cooling nights of late summer/early fall, as the suns angle changes trees “know” when it is time to shut down and hibernate for winter.

Premature coloring on a ash tree branch in Clayton,WI September 5th 2011

Sometimes a tree can exhibit coloring with out anything to do with the shortening days of summer. This is called premature coloring, Insects or disease can be a main factor the premature coloring. It can effect any tree at any given season, but it is most often seen with in about 3-7 weeks before normal fall colors arrives. To name some, Verticillium wilt which is a fungal vascular disease is a major producer of premature fall color in Sugar Maples and Silver Maples, it can cause entire trees or some branches to change color weeks before they normally would. To name another Dutch Elms Disease is a insect born disease that infects elm trees, which can cause elm trees to develop premature color on certain branches or spotty branches throughout the tree. To know that a disease is effecting your tree you would often the premature coloring of certain trees in most years.

Disease is not always the contributor of premature color, it can also be caused by damage to trunk or branches. Damage can occur either in several cases but weed whacking too close to trees trunks is a major cause. Severe damage to the trunk can cause a girdling effect on the tree, causing entire trees to turn color prematurely. To discuss one more issue that causes entire trees to color prematurely, root or drought stress is another why some trees show fall color early, in dry years many stressed trees will change colors and drop their leaves to conserve energy. Root stress or damage can cause the same effect can to be seen, in larger cities, the wrong kind of tree planted in a tiny boulevard space can also cause root stress because the area is not large enough for the tree to pick up enough moisture and nutrients, some times resulting in premature coloring and some dead branches, some trees are effected more then other but this is especially seen in Sugar Maples.
Birch tree shedding of the oldest leaves September 5th Clayton,WI

Sometimes trees will exhibit some color when the shedding of the oldest leaves take place. Some species of trees shed some of their oldest leaves about 2-3 weeks before the initial color change. Although this is seen more often in drier years the same effect normally takes place each time, some color can be seen on the oldest leaves, before they drop. This normally only lasts for 1-3 weeks before the tree sheds the oldest leaves and it’s back to green.

So how to you know if your tree has fall color or disease/insect issues? People should know that with most trees, coloring takes place fairly fast and normally starts at the end of most branches on the tree and moves inward, for the most part causing the entire tree to have color at one time. Trees turning in fall do not normally have fall color on just one or two branches or sections of the tree. For premature coloring causes by insects or disease, Look for dead branches, lots of dead branches on a trees that seem to turn early can be a sure sign of diseases. Also look for trunk damage, on weed whipped damaged trees the damage would be most prevalent near the ground level. In cities if you see trees that turn early with lots of pavement around the roots with very little room, this can be a sign of root stress that may cause trees to turn early. Finally for trees that are just shedding look for spotty leaves all over the tree that may be turning that may appear to be the leaves closest to the inner branches.