A Muted Foliage Season—

Excess Summer Rain Leads To Early Leaf Drop

By Nancy K. Crevier

It is not unexpected to see leaves drifting off of trees in the autumn, but this year, more leaves than usual are dropping to the ground, earlier in the season than usual. In some regions of New England, including the central and northern counties of Connecticut, a muted, sparse display of foliage paints the hillsides.

“We started getting phone calls a few weeks ago,” said Dawn Pettinelli, extension educator with the department of plants and sciences at the University of Connecticut in Storrs. “People were worried that their trees were dropping the leaves before they had completely turned color, or sometimes before the leaves turned [color] at all.”

No one is imagining things, she said. Trees have been losing their leaves sooner this fall than they normally would and the reason for it is one over which there is little control: the humid, wet summer experienced this year. “We had excessive precipitation,” said Ms Pettinelli. “Not so much the volume of rain, but the fact that it was constantly misting or raining. The leaves got wet and stayed wet.” That, she said, is a perfect setup for many leaf and tree diseases. Maple trees in particular have been affected by the wet summer.

“A lot of the maples got anthracnose, and because their colorful foliage is so prominent in the fall, it is most obvious to people [when those trees lose their leaves early],” she said. Homeowners may have noticed that maple trees afflicted with anthracnose presented sparsely this summer, with leaves that did not fully expand, some completely leafless branches, and tiny fungal spots dotting the leaves. Tar spot is another maple leaf disease that thrives in the rainy weather, and is pretty much what it sounds like, said Ms Pettinelli. “Big, black spots appear on the leaves, and the weakened tree drops its leaves early.”

Some trees, such as the castura tree or the ash, are designed by nature to drop most of their leaves at one time. Most other deciduous trees lose leaves gradually over the course of the season. When leaves drop before a photosynthesis cycle is completed, chlorophyll, the green coloring in leaves, does not have time to pull back into the tree to reveal the hidden reds, golds, and yellows that people expect to see in the fall. For maples and birch that lose great quantities of leaves before they have turned color, this poses a problem that goes beyond the esthetic loss.

Trees that lose leaves prematurely do not finish the photosynthesis sequence, a food producing reaction in trees. A complete photosynthesis sequence is vital for trees to produce the sugars and carbohydrates that see it through the winter and prepare the tree to put out leaves in the spring, said Ms Pettinelli.

That means that this fall’s damage could extend into next spring. “A stressful winter and any insect and disease infestation in the spring, and a tree will not have the reserves to withstand it,” she said. On the other hand, a mild winter will give diseased trees a chance to recuperate. “We’ll see the results in the spring,” she said.

Unfortunately, there is not much homeowners can do to help the situation this fall, said Ms Pettinelli. “Homeowners can make sure that if a month or more goes by this fall without rain, that they water the [diseased] trees well. Another thing is to be aware that the root system of a tree is as wide as the crown. Don’t park cars on that area, or walk on it if the soil is very wet. Don’t compact the soil there.”

While fertilizers are not food for trees, the right one can help the tree to produce food, much as people take vitamins to enhance the foods that they eat, said Ms Pettinelli. “The problem is, people ignore the needs of trees until the tree is in a decline, and then it is more difficult to help the tree. Because they are so big, people forget that they are plants, and need to be taken care of like one.”

There is a small upside to this foliage season, said Ms Pettinelli. “A late first frost has kept what leaves there are on the trees longer.” And raking season will end early.