Can it really be fall if the leaves haven?t fallen off the trees?

The falling snow, the lakes freezing over, the frost on the windshield, the geese and ducks flying south and deer season all tell us it must be fall in northern Minnesota. Then why do so many of the hardwood trees still have leaves? The leaves are dead. They are brown or some shade of sickly green. They are also dry and crumbly, but they are still attached to many of the trees. Shaking the tree doesn?t dislodge the leaves, the petiole is still firmly attached to the tree.

This is not expected to have any adverse affect on the trees next year. However, if we get a freezing rain followed with wet snow that sticks to the trees, it is possible that the trees with leaves still attached could suffer more branch breakage due to the extra weight of the snow sticking to the leaves.

One suggestion to explain this phenomenon might be that a hard frost killed the leaves before the abscission layer was fully developed. Here?s the reasoning. The first three weeks of September were very warm with temperatures in the 80's and 90's common across the state. The last week of September cooled off with high temperatures in northern Minnesota in the 60's. Only a few low laying areas of northern Minnesota experienced a killing frost in September. Cold weather came quickly in October with lows moving into the upper 20's the first week and into the mid to low 20's in the second week. Perhaps the warm temperatures delayed formation of the abscission layer and the frosts in early October killed the leaves before the abscission layer was fully formed.

If you have a better guess or actually know why leaves stayed on trees this year we would like to hear from you.